ELECTRONICS AND COMMUNICATION PAGE 2
Contributed by Mercy Benyl
101) what are Semiconductors? Give examples? The materials whose electrical property lies between those of conductors and insulators are known as Semiconductors. Ex germanium, silicon.
102) What are the types of Semiconductor? Intrinsic semiconductor and extrinsic semiconductor.
103) What is Intrinsic Semiconductor? Pure form of semiconductors are said to be intrinsic semiconductor. Ex: germanium, silicon.
104) Give the expression for concentration of electrons.
n = Nc e – (Ec – EF) / KT
Where Nc = 2(2πmnkT\h2)3/2 (1.60 x 10 -19)3/2
105) Give the expression for concentration of Holes.
p = Nv e – (EF – Ev) / KT
Where Nv = 2(2πmpkT\h2)3/2 (1.60 x 10 -19)3/2
106) Give the expression for intrinsic concentration
ni2 = A0T3e-EG0/kT
107) Give the expression for Fermi Dirac probability function?
f(E) = 1 \ 1+ e (E – EF) / KT
108) Define Mass – action law. Under thermal equilibrium the product of free electron concentration (n) and hole concentration (p) is constant regardless of the individual magnitude. n.p = ni2
109) What is mobility? What is its unit? Mobility of the charge carrier is defines as the average drift velocity per unit electricfield. Its unit is meters per volt – seconds. µ = v / E Where µ – mobility v – Drift velocity E – applied electric field
110) Define Conductivity. Conductivity is defined as the current density per unit applied electric field. Its unit is mho per meter
σ = J / E, Where σ – Conductivity J- Current density E - applied electric field
111) Give the relationship between mobility and conductivity .
σ = q n µ, Where σ – Conductivity q- charge of electron n- concentration of electron µ – Mobility
112) Define drift current? When an electric field is applied across the semiconductor, the holes move towards the negative terminal of the battery and electron move towards the positive terminal of the battery. This drift movement of charge carriers will result in a current termed as drift current.
113) What is a transducer and transponder? A transducer is a device, usually electrical, electronic, electromechanical, electromagnetic, photonic, or photovoltaic that converts one type of energy or physical attribute to another for various purposes including measurement or information transfer. In telecommunication, the term transponder (short-for Transmitter-responder and sometimes abbreviated to XPDR, XPNDR, TPDR or TP) has the following meanings:
• An automatic device that receives, amplifies, and retransmits a signal on a different frequency (see also broadcast translator).
• An automatic device that transmits a predetermined message in response to a predefined received signal.
• A receiver-transmitter that will generate a reply signal upon proper electronic interrogation.
A communications satellite’s channels are called transponders, because each is a separate transceiver or repeater.
114) Distinguish between Angle modulation and Amplitude modulation. In amplitude Modulation as the amplitude of given signal varies, the amplitude of carrier signal also varies in the same way. In angle modulation, the frequency or phase may vary according to the amplitude of given signal
115) Define the term diffusion current? A concentration gradient exists, if the number of either electrons or holes is greater in one region of a semiconductor as compared to the rest of the region. The holes and electron tend to move from region of higher concentration to the region of lower concentration. This process in called diffusion and the current produced due this movement is diffusion current.
116) Give the expression for diffusion current density due to electron.
Jn = q Dn dn / dx Where
Jn - diffusion current density due to electron,
q - charge of an electron
Dn – diffusion constant for electron
dn / dx – concentration gradient
117) Give the expression for diffusion current density due to holes.
Jp = - q Dp dp / dx, Where
Jp - diffusion current density due to holes, q - Charge of a hole, Dp – diffusion constant for hole, dn / dx – concentration gradient
118) Define mean life time of a hole or and electron. The electron hole pair created due to thermal agitation will disappear as a result of recombination. Thus an average time for which a hole or an electron exist before recombination can be said as the mean life time of a hole or electron.
119) What is barrier potential? Because of the oppositely charged ions present on both sides of PN junction an electric potential is established across the junction even without any external voltage source which is termed as barrier potential.
120) Why a contact difference of potential exist in PN junction? when a pn junction is formed by placing a p-type and n-type material in intimate contact, the Fermi level throughout the newly formed specimen is not constant at equilibrium. There will be transfer of electron and energy until Fermi levels in the two side did line up. But the valence and conduction band in p side cannot be at the at the same level as in n side .this shift in energy level results in contact difference of potential .
121) Give the expression of contact difference of potential? E0 = kT ln ND NA / ni2, where E0 - contact difference of potential, K – Boltzmann constant, T – Temperature, ND - concentration of donor atoms, NA - concentration of acceptor atoms, ni – intrinsic concentration
122) What is the other name of continuity equation? What does it indicate? The other name of continuity equation is equation of conservation of charge. This equation indicates that the rate at which holes are generated thermally just equals the rate at which holes are lost because of recombination under equilibrium conditions.
123) Give the expression for continuity equation?
dp / dt = - (p-p0)/τp + Dp d2p / dx2 - µp d(pE) / dx
Where, Dp – diffusion constant for hole, µp – mobility of holes
124) What is the basic difference between Latches and Flip flops? latch works without clock signal, but works with a control signal and it is level triggered device, whereas flip flop is a 1 bit storage element and works with a clock signal. Its a edge triggered device. normally latches are avoided and flip flops are preferred.
125) what is Barkhausen Criterion? 1./AB/=1,i.e. the magnitude of loop gain must be unity 2.the total prase shift around the closed loop is zero or 360 degrees.
126) What is MIMO ? MIMO (multiple input, multiple output) is an antenna technology for wireless communications in which multiple antennas are used at both the source (transmitter) and the destination (receiver). The antennas at each end of the communications circuit are combined to minimize errors and optimize data speed. MIMO is one of several forms of smart antenna technology, the others being MISO (multiple input, single output) and SIMO (single input, multiple output)
127) What is capacitor? A capacitor is an electrical/electronic device that can store energy in the electric field between a pair of conductors (called "plates"). The process of storing energy in the capacitor is known as "charging", and involves electric charges of equal magnitude, but opposite polarity, building up on each plate. Capacitors are often used in electric and electronic circuits as energy-storage devices. They can also be used to differentiate between high-frequency and low-frequency signals. This property makes them useful in electronic filters. Capacitors are occasionally referred to as condensers. This term is considered archaic in English, but most other languages use acognate of condenser to refer to a capacitor.
128) What is inductor? An inductor is a passive electrical device employed in electrical circuits for its property of inductance. An inductor can take many forms.
129) Give the value of Charge, Mass of an electron.
Charge of an electron – 1.6 x 10 -19 coloumbs Mass of an electron - 9.11 x 10 -31 Kgs
130) What is Electrostatic deflection sensitivity? Electrostatic deflection sensitivity of a pair of deflecting plates of a cathode ray oscilloscope ( CRO) is defined as the amount of deflection of electron spot produced when a voltage of 1 Volt DC is applied between the corresponding plates.
131) Define Grown junction. A junction obtained by drawing a single crystal from a melt of germanium whose type is changed during the drawing process by adding first P-type and then n –type impurity is called as grown junction.
132) What is a varactor diode? A diode which is based on the voltage variable capacitance of the reverse biased p-n junction is said to be varactor diode. It has other names such as varicaps, voltacaps.
133) Give the expression for charge control description of a diode.
Charge control description of a diode can be given by I = Q /τp
Where I – current across the diode , Q – stored charge, τp - L2p / Dp – life time for holes
134) What is recovery time? Give its types. When a diode has its state changed from one type of bias to other a transient accompanies the diode response, i.e., the diode reaches steady state only after an interval of time “ tr” called as recovery time. The recovery time can be divided in to two types such as forward recovery time and reverse recovery time
135) What is meant by forward recovery time? The forward recovery time may be defined as the time interval from the instant of 10% diode voltage to the instant this voltage reaches 90% of the final value. It is represented as t f r.
136) What is meant by reverse recovery time? The reverse recovery time can be defined as the time required for injected or the excess minority carrier density reduced to zero , when external voltage is suddenly reversed.
137) Give the expression for Electrostatic deflection sensitivity? SE = l x D \ 2 x S x Va where l – length of the plates , D – distance between the centre of the plate and screen , S – distance between the plates , Va - anode potential.
138) What is Cyclotron? Cyclotron is a device that imparts very high energies to positive ions. These higher energy positive ions are then allowed to bombard some substances, which become radioactive and generally disintegrate.
139) Give the expression for frequency of Cyclotron? f = e x B / 2 x π x m Hz
140) What is op-amp? An operational amplifier, often called an op-amp , is a DC-coupled high-gain electronic voltage amplifier with differential inputs and, usually, a single output. Typically the output of the op-amp is controlled either by negative feedback, which largely determines the magnitude of its output voltage gain, or by positive feedback, which facilitates regenerative gain and oscillation.
141) what is the difference between SCR and diode rectifier? diode is a 2 terminal device, in scr gate controls the rectifing. SCR is used in High frequency applications but diode is low frequency devices, SCR can be in high temperatures but not diode.
142) What is a metal semiconductor contact? A metal semiconductor contact is a contact between a metal and a semiconductor which according to the doping level and requirement may act as a rectifying diode or just a simple contact between a semiconductor device and the outside world.
143) What are the two types of metal semiconductor contact?
a. Ohmic type – it is the type of contact designed when lead to be attached to a semiconductor
b. Rectifying type – rectifying type results in a metal semiconductor diode.
144) Define work function. Work function is defined as the energy difference between the Fermi level and the vacuum level in the energy band of the metal or a semiconductor.
145) Define electron affinity. Electron affinity can be defined as the energy difference between the conduction band edge and the vacuum level in the semiconductors.
146) Define contact potential in metal semiconductor contact. The difference of potential between the work function of metal and the work function of semiconductor in a metal semiconductor contact is termed as contact potential.
147) What is a schottky diode? A special type of diode which is manufactured for high frequency (> 10 MHZ) rectifying action and for fast switching is called as schottky diode. It is formed by connecting a metal and a semiconductor along with the ohmic contacts.
148) what is intersymbol interference? In telecommunication, intersymbol interference (ISI) means a form of distortion of a signal that causes the previously transmitted symbols to have an effect on the currently received symbol. This is usually an unwanted phenomenon as the previous symbols have similar effect as noise, thus making the communication less reliable. ISI is usually caused by echoes or non-linear frequency response of the channel. Ways to fight against intersymbol interference include adaptive equalization or error correcting codes (especially soft-decoding with Viterbi algorithm).
149) Give the applications of schottky diode.
b. It can switch off faster than bipolar diodes
c. It is used to rectify very high frequency signals (>10 MHZ)
d. as a switching device in digital computers.
e. It is used in clipping and clamping circuits.
f. It is used in communication systems such as frequency mixers, modulators and detectors.
150) What are active components? The components which produce the energy in the form of current or voltage are called as active components. Example: transistors etc,.
102) What are the types of Semiconductor? Intrinsic semiconductor and extrinsic semiconductor.
103) What is Intrinsic Semiconductor? Pure form of semiconductors are said to be intrinsic semiconductor. Ex: germanium, silicon.
104) Give the expression for concentration of electrons.
n = Nc e – (Ec – EF) / KT
Where Nc = 2(2πmnkT\h2)3/2 (1.60 x 10 -19)3/2
105) Give the expression for concentration of Holes.
p = Nv e – (EF – Ev) / KT
Where Nv = 2(2πmpkT\h2)3/2 (1.60 x 10 -19)3/2
106) Give the expression for intrinsic concentration
ni2 = A0T3e-EG0/kT
107) Give the expression for Fermi Dirac probability function?
f(E) = 1 \ 1+ e (E – EF) / KT
108) Define Mass – action law. Under thermal equilibrium the product of free electron concentration (n) and hole concentration (p) is constant regardless of the individual magnitude. n.p = ni2
109) What is mobility? What is its unit? Mobility of the charge carrier is defines as the average drift velocity per unit electricfield. Its unit is meters per volt – seconds. µ = v / E Where µ – mobility v – Drift velocity E – applied electric field
110) Define Conductivity. Conductivity is defined as the current density per unit applied electric field. Its unit is mho per meter
σ = J / E, Where σ – Conductivity J- Current density E - applied electric field
111) Give the relationship between mobility and conductivity .
σ = q n µ, Where σ – Conductivity q- charge of electron n- concentration of electron µ – Mobility
112) Define drift current? When an electric field is applied across the semiconductor, the holes move towards the negative terminal of the battery and electron move towards the positive terminal of the battery. This drift movement of charge carriers will result in a current termed as drift current.
113) What is a transducer and transponder? A transducer is a device, usually electrical, electronic, electromechanical, electromagnetic, photonic, or photovoltaic that converts one type of energy or physical attribute to another for various purposes including measurement or information transfer. In telecommunication, the term transponder (short-for Transmitter-responder and sometimes abbreviated to XPDR, XPNDR, TPDR or TP) has the following meanings:
• An automatic device that receives, amplifies, and retransmits a signal on a different frequency (see also broadcast translator).
• An automatic device that transmits a predetermined message in response to a predefined received signal.
• A receiver-transmitter that will generate a reply signal upon proper electronic interrogation.
A communications satellite’s channels are called transponders, because each is a separate transceiver or repeater.
114) Distinguish between Angle modulation and Amplitude modulation. In amplitude Modulation as the amplitude of given signal varies, the amplitude of carrier signal also varies in the same way. In angle modulation, the frequency or phase may vary according to the amplitude of given signal
115) Define the term diffusion current? A concentration gradient exists, if the number of either electrons or holes is greater in one region of a semiconductor as compared to the rest of the region. The holes and electron tend to move from region of higher concentration to the region of lower concentration. This process in called diffusion and the current produced due this movement is diffusion current.
116) Give the expression for diffusion current density due to electron.
Jn = q Dn dn / dx Where
Jn - diffusion current density due to electron,
q - charge of an electron
Dn – diffusion constant for electron
dn / dx – concentration gradient
117) Give the expression for diffusion current density due to holes.
Jp = - q Dp dp / dx, Where
Jp - diffusion current density due to holes, q - Charge of a hole, Dp – diffusion constant for hole, dn / dx – concentration gradient
118) Define mean life time of a hole or and electron. The electron hole pair created due to thermal agitation will disappear as a result of recombination. Thus an average time for which a hole or an electron exist before recombination can be said as the mean life time of a hole or electron.
119) What is barrier potential? Because of the oppositely charged ions present on both sides of PN junction an electric potential is established across the junction even without any external voltage source which is termed as barrier potential.
120) Why a contact difference of potential exist in PN junction? when a pn junction is formed by placing a p-type and n-type material in intimate contact, the Fermi level throughout the newly formed specimen is not constant at equilibrium. There will be transfer of electron and energy until Fermi levels in the two side did line up. But the valence and conduction band in p side cannot be at the at the same level as in n side .this shift in energy level results in contact difference of potential .
121) Give the expression of contact difference of potential? E0 = kT ln ND NA / ni2, where E0 - contact difference of potential, K – Boltzmann constant, T – Temperature, ND - concentration of donor atoms, NA - concentration of acceptor atoms, ni – intrinsic concentration
122) What is the other name of continuity equation? What does it indicate? The other name of continuity equation is equation of conservation of charge. This equation indicates that the rate at which holes are generated thermally just equals the rate at which holes are lost because of recombination under equilibrium conditions.
123) Give the expression for continuity equation?
dp / dt = - (p-p0)/τp + Dp d2p / dx2 - µp d(pE) / dx
Where, Dp – diffusion constant for hole, µp – mobility of holes
124) What is the basic difference between Latches and Flip flops? latch works without clock signal, but works with a control signal and it is level triggered device, whereas flip flop is a 1 bit storage element and works with a clock signal. Its a edge triggered device. normally latches are avoided and flip flops are preferred.
125) what is Barkhausen Criterion? 1./AB/=1,i.e. the magnitude of loop gain must be unity 2.the total prase shift around the closed loop is zero or 360 degrees.
126) What is MIMO ? MIMO (multiple input, multiple output) is an antenna technology for wireless communications in which multiple antennas are used at both the source (transmitter) and the destination (receiver). The antennas at each end of the communications circuit are combined to minimize errors and optimize data speed. MIMO is one of several forms of smart antenna technology, the others being MISO (multiple input, single output) and SIMO (single input, multiple output)
127) What is capacitor? A capacitor is an electrical/electronic device that can store energy in the electric field between a pair of conductors (called "plates"). The process of storing energy in the capacitor is known as "charging", and involves electric charges of equal magnitude, but opposite polarity, building up on each plate. Capacitors are often used in electric and electronic circuits as energy-storage devices. They can also be used to differentiate between high-frequency and low-frequency signals. This property makes them useful in electronic filters. Capacitors are occasionally referred to as condensers. This term is considered archaic in English, but most other languages use acognate of condenser to refer to a capacitor.
128) What is inductor? An inductor is a passive electrical device employed in electrical circuits for its property of inductance. An inductor can take many forms.
129) Give the value of Charge, Mass of an electron.
Charge of an electron – 1.6 x 10 -19 coloumbs Mass of an electron - 9.11 x 10 -31 Kgs
130) What is Electrostatic deflection sensitivity? Electrostatic deflection sensitivity of a pair of deflecting plates of a cathode ray oscilloscope ( CRO) is defined as the amount of deflection of electron spot produced when a voltage of 1 Volt DC is applied between the corresponding plates.
131) Define Grown junction. A junction obtained by drawing a single crystal from a melt of germanium whose type is changed during the drawing process by adding first P-type and then n –type impurity is called as grown junction.
132) What is a varactor diode? A diode which is based on the voltage variable capacitance of the reverse biased p-n junction is said to be varactor diode. It has other names such as varicaps, voltacaps.
133) Give the expression for charge control description of a diode.
Charge control description of a diode can be given by I = Q /τp
Where I – current across the diode , Q – stored charge, τp - L2p / Dp – life time for holes
134) What is recovery time? Give its types. When a diode has its state changed from one type of bias to other a transient accompanies the diode response, i.e., the diode reaches steady state only after an interval of time “ tr” called as recovery time. The recovery time can be divided in to two types such as forward recovery time and reverse recovery time
135) What is meant by forward recovery time? The forward recovery time may be defined as the time interval from the instant of 10% diode voltage to the instant this voltage reaches 90% of the final value. It is represented as t f r.
136) What is meant by reverse recovery time? The reverse recovery time can be defined as the time required for injected or the excess minority carrier density reduced to zero , when external voltage is suddenly reversed.
137) Give the expression for Electrostatic deflection sensitivity? SE = l x D \ 2 x S x Va where l – length of the plates , D – distance between the centre of the plate and screen , S – distance between the plates , Va - anode potential.
138) What is Cyclotron? Cyclotron is a device that imparts very high energies to positive ions. These higher energy positive ions are then allowed to bombard some substances, which become radioactive and generally disintegrate.
139) Give the expression for frequency of Cyclotron? f = e x B / 2 x π x m Hz
140) What is op-amp? An operational amplifier, often called an op-amp , is a DC-coupled high-gain electronic voltage amplifier with differential inputs and, usually, a single output. Typically the output of the op-amp is controlled either by negative feedback, which largely determines the magnitude of its output voltage gain, or by positive feedback, which facilitates regenerative gain and oscillation.
141) what is the difference between SCR and diode rectifier? diode is a 2 terminal device, in scr gate controls the rectifing. SCR is used in High frequency applications but diode is low frequency devices, SCR can be in high temperatures but not diode.
142) What is a metal semiconductor contact? A metal semiconductor contact is a contact between a metal and a semiconductor which according to the doping level and requirement may act as a rectifying diode or just a simple contact between a semiconductor device and the outside world.
143) What are the two types of metal semiconductor contact?
a. Ohmic type – it is the type of contact designed when lead to be attached to a semiconductor
b. Rectifying type – rectifying type results in a metal semiconductor diode.
144) Define work function. Work function is defined as the energy difference between the Fermi level and the vacuum level in the energy band of the metal or a semiconductor.
145) Define electron affinity. Electron affinity can be defined as the energy difference between the conduction band edge and the vacuum level in the semiconductors.
146) Define contact potential in metal semiconductor contact. The difference of potential between the work function of metal and the work function of semiconductor in a metal semiconductor contact is termed as contact potential.
147) What is a schottky diode? A special type of diode which is manufactured for high frequency (> 10 MHZ) rectifying action and for fast switching is called as schottky diode. It is formed by connecting a metal and a semiconductor along with the ohmic contacts.
148) what is intersymbol interference? In telecommunication, intersymbol interference (ISI) means a form of distortion of a signal that causes the previously transmitted symbols to have an effect on the currently received symbol. This is usually an unwanted phenomenon as the previous symbols have similar effect as noise, thus making the communication less reliable. ISI is usually caused by echoes or non-linear frequency response of the channel. Ways to fight against intersymbol interference include adaptive equalization or error correcting codes (especially soft-decoding with Viterbi algorithm).
149) Give the applications of schottky diode.
b. It can switch off faster than bipolar diodes
c. It is used to rectify very high frequency signals (>10 MHZ)
d. as a switching device in digital computers.
e. It is used in clipping and clamping circuits.
f. It is used in communication systems such as frequency mixers, modulators and detectors.
150) What are active components? The components which produce the energy in the form of current or voltage are called as active components. Example: transistors etc,.
151) What is difference between Microprocessor and Microcontroller ?
Microprocessors generally require external components to implement program memory, ram memory and Input/output. Intel's 8086, 8088, and 80386 are examples of microprocessors. Micro controllers incorporate program memory, ram memory and input/output resources internal to the chip. Microchip's pic series and Atmel's AVR series are examples of micro controllers.
152) Why is Zener Diode always used in Reverse Bias condition ?
When biased in the forward direction it behaves just like a normal signal diode passing the rated current, but when a reverse voltage is applied to it the reverse saturation current remains fairly constant over a wide range of voltages. The reverse voltage increases until the diodes breakdown voltage VB is reached at which point a process called Avalanche Breakdown occurs in the depletion layer and the current flowing through the zener diode increases dramatically to the maximum circuit value (which is usually limited by a series resistor). This breakdown voltage point is called the "zener voltage" for zener diodes.
153) What is a DIAC?
DIAC is a two terminal bidirectional semiconductor switching device. . It can conduct in either direction depending upon the polarity of the voltage applied across its main terminals. In operation DIAC is equivalent to two 4 layer diodes connected in antiparallel.
154) Give some applications of DIAC.
(a). to trigger TRIAC
(b). Motor speed control
(c). Heat control
(d). Light dimmer circuits
155) What is Biasing? biasing is a process of connecting dc voltage to a device by which we can select the operating point of the device. by biasing actually we select the operating point of the device.
156) What is meant by pre-emphasis and de-emphasis? Pre-emphasis " Improving the signal to noise ratio by increasing the magnitude of higher frequency signals with respect to lower frequency signals" De-emphasis " Improving the signal to noise ratio by decreasing the magnitude of higher frequency signals with respect to lower frequency signals"
157) What is Race-around problem? How can you rectify it? A condition in logic network in which the difference in propagation times through two or more signal paths in the network can produce an erroneous output.in jk flip flop race around problem will occur when both the inputs are high. it can be prevented by using master slave jk flip flop
158) What is a tunnel diode?
The tunnel diode is a pn junction diode in which the impurity concentration is greatly increased about 1000 times higher than a conventional PN junction diode thus yielding a very thin depletion layer. This diode utilizes a phenomenon called tunneling and hence the diode is referred as tunnel diode.
159) What is tunneling phenomenon?
The phenomenon of penetration of the charge carriers directly though the potential barrier instead of climbing over it is called as tunneling.
160) What is backward diode?
The backward diode is a diode in which the doping level is moderate. The forward current in this case is very small, very much similar to that of the reverse current in the conventional diode.
161) What do you mean by an ideal voltage source?
In electric circuit theory, an ideal voltage source is a circuit element where the voltage across it is independent of the current through it. Sources infinite current to any load without any change in o/p voltage.
162) What do you mean by zener breakdown and avalanche breakdown?
Zener breakdown In Zener breakdown the electrostatic attraction between the negative electrons and a large positive voltage is so great that it pulls electrons out of their covalent bonds and away from their parent atoms. ie Electrons are transferred from the valence to the conduction band. In this situation the current can still be limited by the limited number of free electrons produced by the applied voltage so it is possible to cause Zener breakdown without damaging the semiconductor. Avalanche breakdown occurs when the applied voltage is so large that electrons that are pulled from their covalent bonds are accelerated to great velocities. These electrons collide with the silicon atoms and knock off more electrons. These electrons are then also accelerated and subsequently collide with other atoms. Each collision produces more electrons which leads to more collisions etc. The current in the semiconductor rapidly increases and the material can quickly be destroyed.
163) What are the different types of filters?
low pass, high pass, band pass, band stop, resonant
164) What is sampling theorem?
A bandlimited signal can be reconstructed exactly if it is sampled at a rate atleast twice the maximum frequency component in it.
165) What is impulse response? Impulse response is the response of a system to a unit impulse at its input. The impulse response function is the inverse Laplace transform of the system transfer function H(s).
166) Explain the advantages and disadvantages of FIR filters compared to IIR counterparts. IIR filters are recursive and FIR filters are non-recursive. Also FIR filters are linear phase and IIR filters are not. fir filter are highly stable.we can obtain linear phase in fir filter. rounding error is abscent in fir filter.
167) What is CMRR? Explain briefly. The ratio of the gain of an amplifier for difference signals between the input terminals, to the gain for the average or common-mode signal component.
168) What is Transmission Frequency of Bluetooth, Wi-Fi and Wi-MAX ? Bluetooth uses a radio technology called frequency-hopping spread spectrum, which chops up the data being sent and transmits chunks of it on up to 79 bands (1 MHz each) in the range 2402-2480 MHz. This range is in the globally unlicensed Industrial, Scientific and Medical (ISM) 2.4 GHz short-range radio frequency band. between 2.402 GHz and 2.480 GHz, to be exact Wi-Fi stands for Wireless Fidelity. Wi-Fi is based on the IEEE 802.11 family of standards and is primarily a local area networking (LAN) technology designed to provide in-building broadband coverage. WiMAX is an IP based, wireless broadband access technology that provides performance similar to 802.11/Wi-Fi networks with the coverage and QOS (quality of service) of cellular networks. WiMAX is also an acronym meaning "Worldwide Interoperability for Microwave Access (WiMAX). WiMAX is a wireless digital communications system, also known as IEEE 802.16, that is intended for wireless "metropolitan area networks". WiMAX can provide broadband wireless access (BWA) up to 30 miles (50 km) for fixed stations, and 3 - 10 miles (5 - 15 km) for mobile stations. In contrast, the WiFi/802.11 wireless local area network standard is limited in most cases to only 100 - 300 feet (30 - 100m).
169) Define storage time. The interval time for the stored minority charge to become zero is called storage time. It is represented as t s.
170) Define transition time. The time when the diode has normally recovered and the diode reverse current reaches reverse saturaton current I0 is called as transition time. It is represented as t t
171). What are break down diodes? Diodes which are designed with adequate power dissipation capabilities to operate in the break down region are called as break down or zener diodes.
172) What is break down? What are its types? When the reverse voltage across the pn junction is increased rapidly at a voltage the junction breaks down leading to a current flow across the device. This phenomenon is called as break down and the voltage is break down voltage. The types of break down are i) zener break down ii)Avalanche breakdown
173) What is zener breakdown? Zener break down takes place when both sides of the junction are very heavily doped and
Consequently the depletion layer is thin and consequently the depletion layer is tin. When a small value of reverse bias voltage is applied , a very strong electric field is set up across the thin depletion layer. This electric field is enough to break the covalent bonds. Now extremely large number of free charge carriers are produced which constitute the zener current. This process is known as zener break down.
174) What are the various interrupts in 8086? Maskable interrupts, Non-Maskable interrupts
175) What is meant by Maskable interrupts? An interrupt that can be turned off by the programmer is known as Maskable interrupt.
176) Which interrupts are generally used for critical events? Non-Maskable interrupts are used in critical events Such as Power failure, Emergency, Shut off etc.
177) Define the term diffusion capacitance. The diffusion capacitance of a forward biased diode is defined as the rate of change of injected charge with voltage.
CD = τ I / ή VT
Where
τ – time constant I – current across the diode vT – threshold voltage
178) What is the Maximum clock frequency in 8086? 5 Mhz is the Maximum clock frequency in 8086.
179) What are the various segment registers in 8086? Code, Data, Stack, Extra
180) Which Stack is used in 8086? FIFO (First In First Out) stack is used in 8086.In this type of Stack the first stored information is retrieved first.
181) What are the various registers in 8085? Accumulator register, Temporary register, Instruction register, Stack Pointer, Program Counter are the various registers in 8085 .
182) How many interrupts are there in 8085? There are 12 interrupts in 8085.
183) What is clock frequency for 8085? 3 MHz is the maximum clock frequency for 8085.
184) In 8085 which is called as High order / Low order Register? Flag is called as Low order register & Accumulator is called as High order Register.
185) Define Analog and Digital Signal Processing? Analog signal processing is for signals that have not been digitized, as in classical radio, telephone, radar, and television systems. This involves linear electronic circuits such as passive filters, active filters, additive mixers, integrators and delay lines. It also involves non-linear circuits such as compandors, multiplicators (frequency mixers and voltage controlled amplifiers), voltage-controlled filters,voltage-controlled oscillators and phaselocked loops. Discrete time signal processing Discrete time signal processing is for sampled signals that are considered as defined only at discrete points in time, and as such are quantized in time, but not in magnitude. Analog discrete-time signal processing is a technology based on electronic devices such as sample and hold circuits, analog time-division multiplexers, analog delay lines and analog feedback shift registers. This technology was a predecessor of digital signal processing (see below), and is still used in advanced processing of gigahertz signals. The concept of discrete-time signal processing also refers to a theoretical discipline that establishes a mathematical basis for digital signal processing, without taking quantization error into consideration.
186) What is RS in RS-232 ? RS-232 (Recommended Standard - 232) is a telecommunications standard for binary serial communications between devices. It supplies the roadmap for the way devices speak to each other using serial ports. The devices are commonly referred to as a DTE (data terminal equipment) and DCE (data communications equipment); for example, a computer and modem, respectively
187)What is Lenz law ? An induced current is always in such a direction as to oppose the motion or change causing it whenever there is an induced electromotive force (emf) in a conductor, it is always in such a direction that the current it would produce would oppose the change which causes the induced emf. If the change is the motion of a conductor through a magnetic field, the induced current must be in such a direction as to produce a force opposing the motion. If the change causing the emf is a change of flux threading a coil, the induced current must produce a flux in such a direction as to oppose the change.
188). Give the Poisson’s equation relating the potential and the charge density?
d2V / dx2 = e NA / ε
Where
V – Potential e - Charge of the electron NA – acceptor ion concentration ε - Permittivity of material
189) What is ZigBee and its specifications ? ZigBee is a low-cost, low-power, wireless mesh networking standard. First, the low cost allows the technology to be widely deployed in wireless control and monitoring applications. Second, the low power-usage allows longer life with smaller batteries. Third, the mesh networking provides high reliability and more extensive range. ZigBee relies on the basic 802.15.4 standard to establish radio performance
190). What is the static resistance of a diode?
Static resistance R of a diode can be defined as the ratio of voltage V across the diode to the current flowing through the diode.
R = V/ I
Where
R - Static resistance of a diode
V - Voltage across the diode I - current across the diode
191) Define dynamic resistance.
Dynamic resistance of a diode can be defined as the ratio of change in voltage across the diode to the change in current through the diode.
r = ∆ V / ∆ I
Where r - Dynamic resistance of a diode ∆ V - change in voltage across the diode ∆ I - change in current through the diode
192) Define dynamic conductance.
Dynamic conductance of a diode can be defined as the ratio of change in the change in current through the diode to the voltage across the diode. This can also be defined as the inverse of Dynamic resistance.
g = ∆ I / ∆ V = I + I0 / ή vT Where
g - Dynamic conductance of a diode ∆ V - change in voltage across the diode ∆ I - change in current through the diode vT – threshold voltage
193) What is difference between Piconet and Scatternet ? A piconet is the type of connection that is formed between two or more Bluetooth-enabled devices, one device takes the role of 'master', and all other devices assume a 'slave' role for synchronization reasons. Where as a scatternet is a number of interconnected piconets that supports communication between more than 8 devices. Scatternets can be formed when a member of one piconet (either the master or one of the slaves) elects to participate as a slave in a second, separate piconet.
194) What is Moore's Law ? The prediction by Gordon Moore (cofounder of the Intel Corporation) that the number of transistors on a microprocessor would double periodically (approximately every 18 months).
195) How many satellites comprise the GPS and expand it ? The minimum satellites required to track your position is three. That is why it is known as triangulation. Currently, there are 32 satellites in the GPS system. The exact number varies as old satellites fail or are retired, and new satellites are sent up to replace them.
196) On what principle do Transformers work ? A transformer is a static device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual induction.
197) What is EDFA ? Erbium Doped Fiber Amplifier (EDFA) A device that boosts the signal in an optical fiber. EDFA is an optical repeater device that is used to boost the intensity of optical signals being carried through a fiber optic communications system. An optical fiber is doped with the rare earth element erbium so that the glass fiber can absorb light at one frequency and emit light at another frequency. An external semiconductor laser couples light into the fiber at infrared wavelengths of either 980 or 1480 nanometers. This action excites the erbium atoms. Additional optical signals at wavelengths between 1530 and 1620 nanometers enter the fiber and stimulate the excited erbium atoms to emit photons at the same wavelength as the incoming signal. This action amplifies a weak optical signal to a higher power, effecting a boost in the signal strength.
198) What is Stack Pointer Stack pointer is a special purpose 16-bit register in the Microprocessor, which holds the address of the top of the stack
199) What is Program counter? Program counter holds the address of either the first byte of the next instruction to be fetched for execution or the address of the next byte of a multi byte instruction, which has not been completely fetched. In both the cases it gets incremented automatically one by one as the instruction bytes get fetched. Also Program register keeps the address of the next instruction.
200) Which Stack is used in 8085? LIFO (Last In First Out) stack is used in 8085.In this type of Stack the last stored information can be retrieved first.
Microprocessors generally require external components to implement program memory, ram memory and Input/output. Intel's 8086, 8088, and 80386 are examples of microprocessors. Micro controllers incorporate program memory, ram memory and input/output resources internal to the chip. Microchip's pic series and Atmel's AVR series are examples of micro controllers.
152) Why is Zener Diode always used in Reverse Bias condition ?
When biased in the forward direction it behaves just like a normal signal diode passing the rated current, but when a reverse voltage is applied to it the reverse saturation current remains fairly constant over a wide range of voltages. The reverse voltage increases until the diodes breakdown voltage VB is reached at which point a process called Avalanche Breakdown occurs in the depletion layer and the current flowing through the zener diode increases dramatically to the maximum circuit value (which is usually limited by a series resistor). This breakdown voltage point is called the "zener voltage" for zener diodes.
153) What is a DIAC?
DIAC is a two terminal bidirectional semiconductor switching device. . It can conduct in either direction depending upon the polarity of the voltage applied across its main terminals. In operation DIAC is equivalent to two 4 layer diodes connected in antiparallel.
154) Give some applications of DIAC.
(a). to trigger TRIAC
(b). Motor speed control
(c). Heat control
(d). Light dimmer circuits
155) What is Biasing? biasing is a process of connecting dc voltage to a device by which we can select the operating point of the device. by biasing actually we select the operating point of the device.
156) What is meant by pre-emphasis and de-emphasis? Pre-emphasis " Improving the signal to noise ratio by increasing the magnitude of higher frequency signals with respect to lower frequency signals" De-emphasis " Improving the signal to noise ratio by decreasing the magnitude of higher frequency signals with respect to lower frequency signals"
157) What is Race-around problem? How can you rectify it? A condition in logic network in which the difference in propagation times through two or more signal paths in the network can produce an erroneous output.in jk flip flop race around problem will occur when both the inputs are high. it can be prevented by using master slave jk flip flop
158) What is a tunnel diode?
The tunnel diode is a pn junction diode in which the impurity concentration is greatly increased about 1000 times higher than a conventional PN junction diode thus yielding a very thin depletion layer. This diode utilizes a phenomenon called tunneling and hence the diode is referred as tunnel diode.
159) What is tunneling phenomenon?
The phenomenon of penetration of the charge carriers directly though the potential barrier instead of climbing over it is called as tunneling.
160) What is backward diode?
The backward diode is a diode in which the doping level is moderate. The forward current in this case is very small, very much similar to that of the reverse current in the conventional diode.
161) What do you mean by an ideal voltage source?
In electric circuit theory, an ideal voltage source is a circuit element where the voltage across it is independent of the current through it. Sources infinite current to any load without any change in o/p voltage.
162) What do you mean by zener breakdown and avalanche breakdown?
Zener breakdown In Zener breakdown the electrostatic attraction between the negative electrons and a large positive voltage is so great that it pulls electrons out of their covalent bonds and away from their parent atoms. ie Electrons are transferred from the valence to the conduction band. In this situation the current can still be limited by the limited number of free electrons produced by the applied voltage so it is possible to cause Zener breakdown without damaging the semiconductor. Avalanche breakdown occurs when the applied voltage is so large that electrons that are pulled from their covalent bonds are accelerated to great velocities. These electrons collide with the silicon atoms and knock off more electrons. These electrons are then also accelerated and subsequently collide with other atoms. Each collision produces more electrons which leads to more collisions etc. The current in the semiconductor rapidly increases and the material can quickly be destroyed.
163) What are the different types of filters?
low pass, high pass, band pass, band stop, resonant
164) What is sampling theorem?
A bandlimited signal can be reconstructed exactly if it is sampled at a rate atleast twice the maximum frequency component in it.
165) What is impulse response? Impulse response is the response of a system to a unit impulse at its input. The impulse response function is the inverse Laplace transform of the system transfer function H(s).
166) Explain the advantages and disadvantages of FIR filters compared to IIR counterparts. IIR filters are recursive and FIR filters are non-recursive. Also FIR filters are linear phase and IIR filters are not. fir filter are highly stable.we can obtain linear phase in fir filter. rounding error is abscent in fir filter.
167) What is CMRR? Explain briefly. The ratio of the gain of an amplifier for difference signals between the input terminals, to the gain for the average or common-mode signal component.
168) What is Transmission Frequency of Bluetooth, Wi-Fi and Wi-MAX ? Bluetooth uses a radio technology called frequency-hopping spread spectrum, which chops up the data being sent and transmits chunks of it on up to 79 bands (1 MHz each) in the range 2402-2480 MHz. This range is in the globally unlicensed Industrial, Scientific and Medical (ISM) 2.4 GHz short-range radio frequency band. between 2.402 GHz and 2.480 GHz, to be exact Wi-Fi stands for Wireless Fidelity. Wi-Fi is based on the IEEE 802.11 family of standards and is primarily a local area networking (LAN) technology designed to provide in-building broadband coverage. WiMAX is an IP based, wireless broadband access technology that provides performance similar to 802.11/Wi-Fi networks with the coverage and QOS (quality of service) of cellular networks. WiMAX is also an acronym meaning "Worldwide Interoperability for Microwave Access (WiMAX). WiMAX is a wireless digital communications system, also known as IEEE 802.16, that is intended for wireless "metropolitan area networks". WiMAX can provide broadband wireless access (BWA) up to 30 miles (50 km) for fixed stations, and 3 - 10 miles (5 - 15 km) for mobile stations. In contrast, the WiFi/802.11 wireless local area network standard is limited in most cases to only 100 - 300 feet (30 - 100m).
169) Define storage time. The interval time for the stored minority charge to become zero is called storage time. It is represented as t s.
170) Define transition time. The time when the diode has normally recovered and the diode reverse current reaches reverse saturaton current I0 is called as transition time. It is represented as t t
171). What are break down diodes? Diodes which are designed with adequate power dissipation capabilities to operate in the break down region are called as break down or zener diodes.
172) What is break down? What are its types? When the reverse voltage across the pn junction is increased rapidly at a voltage the junction breaks down leading to a current flow across the device. This phenomenon is called as break down and the voltage is break down voltage. The types of break down are i) zener break down ii)Avalanche breakdown
173) What is zener breakdown? Zener break down takes place when both sides of the junction are very heavily doped and
Consequently the depletion layer is thin and consequently the depletion layer is tin. When a small value of reverse bias voltage is applied , a very strong electric field is set up across the thin depletion layer. This electric field is enough to break the covalent bonds. Now extremely large number of free charge carriers are produced which constitute the zener current. This process is known as zener break down.
174) What are the various interrupts in 8086? Maskable interrupts, Non-Maskable interrupts
175) What is meant by Maskable interrupts? An interrupt that can be turned off by the programmer is known as Maskable interrupt.
176) Which interrupts are generally used for critical events? Non-Maskable interrupts are used in critical events Such as Power failure, Emergency, Shut off etc.
177) Define the term diffusion capacitance. The diffusion capacitance of a forward biased diode is defined as the rate of change of injected charge with voltage.
CD = τ I / ή VT
Where
τ – time constant I – current across the diode vT – threshold voltage
178) What is the Maximum clock frequency in 8086? 5 Mhz is the Maximum clock frequency in 8086.
179) What are the various segment registers in 8086? Code, Data, Stack, Extra
180) Which Stack is used in 8086? FIFO (First In First Out) stack is used in 8086.In this type of Stack the first stored information is retrieved first.
181) What are the various registers in 8085? Accumulator register, Temporary register, Instruction register, Stack Pointer, Program Counter are the various registers in 8085 .
182) How many interrupts are there in 8085? There are 12 interrupts in 8085.
183) What is clock frequency for 8085? 3 MHz is the maximum clock frequency for 8085.
184) In 8085 which is called as High order / Low order Register? Flag is called as Low order register & Accumulator is called as High order Register.
185) Define Analog and Digital Signal Processing? Analog signal processing is for signals that have not been digitized, as in classical radio, telephone, radar, and television systems. This involves linear electronic circuits such as passive filters, active filters, additive mixers, integrators and delay lines. It also involves non-linear circuits such as compandors, multiplicators (frequency mixers and voltage controlled amplifiers), voltage-controlled filters,voltage-controlled oscillators and phaselocked loops. Discrete time signal processing Discrete time signal processing is for sampled signals that are considered as defined only at discrete points in time, and as such are quantized in time, but not in magnitude. Analog discrete-time signal processing is a technology based on electronic devices such as sample and hold circuits, analog time-division multiplexers, analog delay lines and analog feedback shift registers. This technology was a predecessor of digital signal processing (see below), and is still used in advanced processing of gigahertz signals. The concept of discrete-time signal processing also refers to a theoretical discipline that establishes a mathematical basis for digital signal processing, without taking quantization error into consideration.
186) What is RS in RS-232 ? RS-232 (Recommended Standard - 232) is a telecommunications standard for binary serial communications between devices. It supplies the roadmap for the way devices speak to each other using serial ports. The devices are commonly referred to as a DTE (data terminal equipment) and DCE (data communications equipment); for example, a computer and modem, respectively
187)What is Lenz law ? An induced current is always in such a direction as to oppose the motion or change causing it whenever there is an induced electromotive force (emf) in a conductor, it is always in such a direction that the current it would produce would oppose the change which causes the induced emf. If the change is the motion of a conductor through a magnetic field, the induced current must be in such a direction as to produce a force opposing the motion. If the change causing the emf is a change of flux threading a coil, the induced current must produce a flux in such a direction as to oppose the change.
188). Give the Poisson’s equation relating the potential and the charge density?
d2V / dx2 = e NA / ε
Where
V – Potential e - Charge of the electron NA – acceptor ion concentration ε - Permittivity of material
189) What is ZigBee and its specifications ? ZigBee is a low-cost, low-power, wireless mesh networking standard. First, the low cost allows the technology to be widely deployed in wireless control and monitoring applications. Second, the low power-usage allows longer life with smaller batteries. Third, the mesh networking provides high reliability and more extensive range. ZigBee relies on the basic 802.15.4 standard to establish radio performance
190). What is the static resistance of a diode?
Static resistance R of a diode can be defined as the ratio of voltage V across the diode to the current flowing through the diode.
R = V/ I
Where
R - Static resistance of a diode
V - Voltage across the diode I - current across the diode
191) Define dynamic resistance.
Dynamic resistance of a diode can be defined as the ratio of change in voltage across the diode to the change in current through the diode.
r = ∆ V / ∆ I
Where r - Dynamic resistance of a diode ∆ V - change in voltage across the diode ∆ I - change in current through the diode
192) Define dynamic conductance.
Dynamic conductance of a diode can be defined as the ratio of change in the change in current through the diode to the voltage across the diode. This can also be defined as the inverse of Dynamic resistance.
g = ∆ I / ∆ V = I + I0 / ή vT Where
g - Dynamic conductance of a diode ∆ V - change in voltage across the diode ∆ I - change in current through the diode vT – threshold voltage
193) What is difference between Piconet and Scatternet ? A piconet is the type of connection that is formed between two or more Bluetooth-enabled devices, one device takes the role of 'master', and all other devices assume a 'slave' role for synchronization reasons. Where as a scatternet is a number of interconnected piconets that supports communication between more than 8 devices. Scatternets can be formed when a member of one piconet (either the master or one of the slaves) elects to participate as a slave in a second, separate piconet.
194) What is Moore's Law ? The prediction by Gordon Moore (cofounder of the Intel Corporation) that the number of transistors on a microprocessor would double periodically (approximately every 18 months).
195) How many satellites comprise the GPS and expand it ? The minimum satellites required to track your position is three. That is why it is known as triangulation. Currently, there are 32 satellites in the GPS system. The exact number varies as old satellites fail or are retired, and new satellites are sent up to replace them.
196) On what principle do Transformers work ? A transformer is a static device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual induction.
197) What is EDFA ? Erbium Doped Fiber Amplifier (EDFA) A device that boosts the signal in an optical fiber. EDFA is an optical repeater device that is used to boost the intensity of optical signals being carried through a fiber optic communications system. An optical fiber is doped with the rare earth element erbium so that the glass fiber can absorb light at one frequency and emit light at another frequency. An external semiconductor laser couples light into the fiber at infrared wavelengths of either 980 or 1480 nanometers. This action excites the erbium atoms. Additional optical signals at wavelengths between 1530 and 1620 nanometers enter the fiber and stimulate the excited erbium atoms to emit photons at the same wavelength as the incoming signal. This action amplifies a weak optical signal to a higher power, effecting a boost in the signal strength.
198) What is Stack Pointer Stack pointer is a special purpose 16-bit register in the Microprocessor, which holds the address of the top of the stack
199) What is Program counter? Program counter holds the address of either the first byte of the next instruction to be fetched for execution or the address of the next byte of a multi byte instruction, which has not been completely fetched. In both the cases it gets incremented automatically one by one as the instruction bytes get fetched. Also Program register keeps the address of the next instruction.
200) Which Stack is used in 8085? LIFO (Last In First Out) stack is used in 8085.In this type of Stack the last stored information can be retrieved first.
