Electronics Q&A
1. What is Electrical and Electronics?
Electrical is the flow of electron in a conductor. Eg., cu,al.
Electronics is the flow of electron in a semiconductor. Eg., si,ge.
2. How components are classified in Electronics?
Two types
1. Active Component
2. Passive Component.
3. What is Active Component?
Active components are non-linear.
i.e, the characteristic of the signal vary when passing through active component.
It delivers power.
4. What is Passive Component?
Passive components are linear.
i.e, the characteristic of the signal does not vary when passing through active component.
It consumes power.
5. Example for Active Component?
Diode, Transistor, Integrated Circuit, Thyristor, SCR and Logic Gates.
6. Example for Passive Component?
Resistor, Capacitor and inductor.
7. What are the types of electrical supply?
Two types,
1. Alternating Current(AC)
2. Direct Current(DC).
8. What is Alternating Current?
The electricity flowing in varying voltage or current in a regular time interval. There is a periodical reverse direction of charge takes place.
9. what is direct current?
The electricity flowing in a constant direction and voltage with constant polarity.
10. what is the direction of flow of current and electron?
Current flows from positive terminal to negative terminal.
Electron flows from negative terminal to positive terminal.
11. What is Resistor?
Resistor is a passive component which is used for control the flow of current and to get required voltage drop. It obeys OHMS LAW, V=IR. Four types of resistor.
1. Fixed Resistor
2. Variable Resistor
3.thermistor
4.Light Dependent Resistor(LDR).
12. what is positive temperature coefficient?
Resistance is increase with increase in temperature. Eg., resistor.
13. what is negative temperature coefficient?
Resistance is decrease with increase with temperature. Eg., thermistor.
14. what is LDR?
Resistance is decrease with increase the illumination of light.
15.symbol of resistor?
16. colour coding table for resistor?
Colour
|
First Digit
|
Second Digit
|
Third Digit
|
Multiplier
|
Tolerance
|
Black
|
0
|
0
|
0
|
1
| |
Brown
|
1
|
1
|
1
|
10
|
1%
|
Red
|
2
|
2
|
2
|
100
|
2%
|
Orange
|
3
|
3
|
3
|
1,000
| |
Yellow
|
4
|
4
|
4
|
10,000
| |
Green
|
5
|
5
|
5
|
100,000
| |
Blue
|
6
|
6
|
6
|
1,000,000
| |
Violet
|
7
|
7
|
7
| ||
Grey
|
8
|
8
|
8
| ||
White
|
9
|
9
|
9
| ||
Gold
|
0.1
|
5%
| |||
Silver
|
0.01
|
10%
| |||
Table 1.1 - Resistor Colour Code
| |||||
17. What is resistivity?
Resistivity is the amount of resistance present per unit length. Its unit is ohm.m.
18. What is capacitor?
Capacitor is a two terminal passive component separated by dielectric which is used to stores the electric charge. It is represented as C. its unit is Faraday.
19. How many types of capacitor?
They are three types,
Non- polarized capacitor, polarized capacitor and variable capacitor.
20. How capacitor are classified based on material?
21. Draw the symbol of capacitor?
22. How the capacitor range is varied?
Based on the dielectric material used in it. The capacitor value is varies for GFto fF.
23. What is the formula to find capacitor?
C=Q/V where, C-capacitance, Q-amount of charge, V-voltage across the conductor.
Where, A-area, D-distance between the electrode, K-dielectric Constance.
24. What is dielectric constant?
Dielectric constant (K) is defined as the ratio of permittivity of dielectric material to the permittivity of free space. it varies based on the material.
25. What is permittivity?
Permittivity is a constant proportionality which shows the characteristics of dielectric affected by electric field.
For free space,
For particular material, eo =8.854 x 10-12 farad per meter (F/m) in free space
relative permittivity, er = e / eo
= e (1.13 x 1011)
= e (1.13 x 1011)
26. What is permeability?
Permeability is the measure of magnetic field formation in a material
µ0 = 4Ï€×10−7 ≈ 1.2566370614…×10−6 H·m−1.
27. What is the function of capacitor?
It allows Alternative current or analog signal and blocks direct current.
28. What happen when capacitor connected in AC circuit?
It simply acts as AC impedance. The impedance decrease with increase in frequency.
29. What is the difference between impedance and resistance?
Impedance is used to represent AC resistance which having both real and imaginary part.
Resistance is used to represent DC resistance which having only real part.
30. What are the application of capacitor?
To avoid AC ripples in DC.
To tune particular frequency.
Bypass.
Coupling.
31. What is meant by bypass?
When the source get sudden failure, which may affect the load. To protect the load form sudden failure of source, bypass capacitor is used.
32. What is meant by coupling?
Coupling is the process of transferring energy from one circuit to another or one medium to another.
33. When the polarity is consider in capacitor?
Capacitor value is high, then no need to worry about polarity. i.e. C<1uF
Capacitor value is low, then need to consider about capacitance. i.e. C>=1uF.
34. SI prefix table?
35. What is inductor?
Inductor is a passive electronic component which is used to store energy in the magnetic field. Its unit is Henry.
36. what is the response of inductor with AC signal?
When the frequency increase in AC signal, the impedance increase simultaneously. The response shown below. where, w-angular frequency,
37. what is the function of inductor?
Inductor is used to block AC and allow DC.
38. how to measure a voltage in an inductior?
Fig a. for resistor
Fig b. for inductor
39. Show the combination of LC as a filter?
fig1. Low pass filter
fig2. High pass filter
fig3. Band pass filter
fig4. Band reject filter
L C Filters
| |
40. How should measure the voltage and current using voltmeter?
Voltage should measure across the load. i.e., shunt measurement.
Current should measure by connecting series resistance with load. i.e., series measurement.
41. Why cut-off or corner frequency measured in 3db?
At 3-db, we get half the power. i.e. maximum power we will get at 3db.voltage is proportional to square root of half power.
So, Sqrt(0.5)=0.707 .
42. What is transducer and transponder?
Transducer is a device which is used to transfer one form of energy to another. E.g. sensor. Transponder is a device which is used to receive, amplify and retransmit the signal in wireless communication.
43. How materials are classified?
Based on the conductivity, materials are classified into
Conductor
Semiconductor
Insulator
44. List some of conductor, semiconductor and insulator?
Conductor- aluminum, copper
Semiconductor –silicon, germanium
Insulator-rubber, paper, mica
45. What is conduction band, valance band and forbidden energy gap?
Conduction band is the higher most energy level which is empty or partially filled.
Valance band is the energy level which is fully filled or partially filled.
Forbidden gap is the distance between conduction band and valance band.
46. What is Femi energy level?
Femi energy level present in-between valance and conduction band. Which is present in semiconductor. When temperature or applied voltage increase, the electron from valance band jump to conduction band via femi energy level.
47. Why Femi energy level?
Femi energy level is used to study the velocity of electron flows from valance band to conduction band using the below formula. Where, E-energy, m-mass of electron.
velocity of electron is given by,
48. State ohms law and microscopic ohms law?
Ohms law: at const temperature, current flowing through the conductor is directly proportional to the potential difference across them.
V=IR
Where, V-voltage, I-current, R-resistance.
Microscopic ohms law: current density is defined as the electric current per unit area.
J=I/A
Where, J-current density, I-electric current, A-area.
49. How the materials are differentiated as conductor, semiconductor and insulator?
Based on the distance between valance band and conduction band. i.e. forbidden energy gap.
50. Why semiconductor is used in electronics?
In semiconductor only, we can control the flow of electron based on applied voltage.
51. How semiconductors are classified?
Semiconductor are classified into two types,
1. Intrinsic semiconductor- pure semiconductor (si, ge).
2. Extrinsic semiconductor- impure semiconductor (SiB, GeP)
52. How Extrinsic semiconductor is classified?
1. P type Extrinsic semiconductor- when pure semiconductor is doped with third group element (boron, gallium)
2. N type Extrinsic semiconductor- when pure semiconductor is doped with fifth group element (phosphorous, antimony)
53. What is doping?
The process of adding impurities(other chemical element) in the semiconductor is called doping.
54. What is direct band gap and indirect band gap?
For direct band gap: propagation constant K is same when energy emits from atom and recombination takes place.
For indirect band gap: propagation constant K is differing when energy emits from atom and recombination does not take place.
55. What is meant by recombination?
When the electron falling from conduction band to empty valance band is called recombination.
56. What is the forbidden gap of Si and Ge?
For Si=1.1eV
For Ge=0.7eV.
57. Why silicon is not used for LED?
For the emitting of photon requires direct band gap but Si having indirect band gap. So it is not used for LED.
58. What is the bond present in pure semiconductor and number of electron present at the outer most orbit?
Covalent bond and 4 electron at the outer most ortib.
59. What is the advantage of Si over Ge?
Silicon with stand in higher temperature compare with Germanium.
60. Which is dangerous AC or DC?
if the current value and voltage value is more then AC make heart attack( sudden dead) and DC makes burning bones( man can survive their life).
In AC affects more because of low frequency even though possible to escape because of time varying but not possible when the power is high.
In DC, if current voltage and human body resistance value satisfied the ohms law then it will burns the Bone.
In AC, shock will comes anywhere in the network.
In DC, shock will comes during short circuit. so, when using car batteries don't make short circuit.
In AC affects more because of low frequency even though possible to escape because of time varying but not possible when the power is high.
In DC, if current voltage and human body resistance value satisfied the ohms law then it will burns the Bone.
In AC, shock will comes anywhere in the network.
In DC, shock will comes during short circuit. so, when using car batteries don't make short circuit.
61. What are the components used in electronics?
Diode
Transistor
Thyristor
IC
62. What is diode?
Diode is an unidirectional active component which allow the current in one direction. It act as switch.
63. How diodes are classified?
1. P-n junction diode
2. Avalanche diode
3. Zener Diode
4. LED (light emitting diode)
5. Photo diode.
6. Laser diode.
7. Varicap diode.
8. Gunn diode.
9. Tunnel diode.
10. PIN diode.
11. Schottky diode.
12. Point contact diode.
13. Crystal diode.
14. Step recovery diode.
15. Transient voltage suppression diode.
16. Constant current diode.
17. Super barrier diode.
64. How a normal p-n junction diode formed?
Diode is made from a single piece of semiconductor material which has a positive P region at one end and negative N region at another end. At the middle diffusion region is formed.
65. What is meant by diffusion?
The process of transfer of electron and holes across each other to form a junction is called diffusion.
66. What is meant by depletion region?
Due to the diffusion, there is a potential barrier formed at the junction to maintain the equilibrium of electrons and holes in N and P region is called depletion layer.
67. What is forward bias?
When the external voltage positive terminal is connected to anode of diode and negative terminal is connected to cathode of diode. Then supply the external voltage is called forward bias. The diode makes closed circuit during forward bias.
68. What is reverse bias?
When the external voltage negative terminal is connected to anode of diode and positive terminal is connected to cathode of diode. Then supply the external voltage is called reverse bias. The diode makes open circuit during reverse bias.
69. What is meant by breakdown?
When the applied reverse bias voltage breaks the junction in diode is called breakdown.
70. How many types of break down?
1. Zener breakdown.
2. Avalanche breakdown.
71. What is meant by zener breakdown?
When both sides of PN junction are heavily doped and the depletion layer is narrow. When a small reverse bias is applied, a strong electric field produced across the junction is called zener breakdown.
72. What is meant avalanche break down?
When both sides of PN junction are lightly doped and the depletion layer is wide. When a small reverse bias is applied, minority carriers accelerated by the field at junction is called avalanche breakdown.
73. Draw the symbol of diode?
74. Show the characteristics of diode?
1. Zero bias
2. Forward bias
3. Reverse bias
75. What is the use of p-n junction diode?
Electronic switch
Amplifier
Rectification
Pulse shaping.
76. What is Zener Diode?
Zener diode is a specially designed PN junction to operate in reverse bias region.
77. What is the use of zener diode?
Regulator
Stabilization
Voltage Reference
Over voltage protection.
78. What is tunnel diode?
A heavily doped PN junction diode is called tunnel diode. Its having special characteristic of negative resistance region.
79. What is meant by negative resistance region?
Due to the quantum effect , when the voltage increase in forward bias, there a current drop occur is called negative resistance region.
80. What is the use of tunnel diode?
RF and micro wave power monitoring.
High frequency trigger.
Detector log video amplifier (DLVA)
Oscillator
It having high resistance with nuclear radiation. So used in amplification for space communication.
81. What is meant by avalanche diode?
Avalanche diode is high sensitive photo diode.
Breakdown takes place based on impact ionization.
It is classified into two types,
IMPATT and TRAPATT diodes
82. What is meant by impact ionization?
The charge carrier lose its energy because of the creation of new charge carrier is called impact ionization.
83. What is the use of Avalanche diode?
It is used to prevent the current concentration at hot spot.
Voltage reference.
RF and microwave generator.
84. What is LED?
Light Emitting Diode is a type of diode which is used to generate photon when the holes and electrons recombine with each other.
85. What is the wavelength produced by LED?
LED can produce the wavelength in the range of visible, UV and infra red.
86. What is meant by electroluminescence?
The process of emission of photon because of the recombination of electron and holes is called electroluminescence.
87. What are the materials used to generate different lights?
88. What is the use of LED?
It is used to display the output.
Transmission of data using LED in fiber and wireless communication.
89. What is photo diode?
Photo diode is a type of diode in which the conversation of light energy into electrical energy takes place. Eg. Solar cell.
90. What are the types of photo diode?
1. p-n photo diode.
2. pin photo diode.
3. Schottky photo diode.
4. Avalanche Photo diode.
91. What is the use of photo diode?
Detection purpose.
Generating power using solar cell.
92. What is laser diode?
A semiconductor component that produce a coherent radiation is called laser diode.
93. What is the use of laser diode?
Medical application.
Detection of damage.
Data transmission in fiber and wireless communication.
94. what are the material used to generate laser?
The most common semiconductors used in laser diodes are compounds based on gallium arsenide (750 to 900 nm in the infrared), indium gallium arsenide phosphide (1200 to 1700 nm in the infrared) and gallium nitride (near 400 nm in the blue).
95. What is varicap diode?
Varicap diode id a diode which is used as a capacitor under reverse bias condition. It is used as a voltage controlled capacitor.
96. What is the application of varicap diode?
It is used in
Amplifier,
Oscillator,
Phase lock loop,
Frequency synthesizer.
97. What is Gunn diode?
Gunn diode is a N-type heavily doped material which having two n+ doped material, in between it there is a n type material. Its having two electrode and exhibit negative resistance.
98. What is the use of Gunn diode?
It is used in high frequency RF application
It is used as a oscillator.
99. show the structure and symbol of gunn diode?
structure
symbol
100. What is tunnel diode?
Tunnel diode is a heavily doped p-n junction diode of a size 10nm. It exhibit negative resistance characteristics during forward bias. Its based on quantum mechanism.
101. What is quantum mechanism?
Quantum mechanism is the study of characteristics of dual particle and wave like behavior, interaction of energy and matter.
102. What is the application of Tunnel diode?
Oscillator in UHF(ultra high frequency) television tuner.
Trigger circuit.
High speed counter circuits.
103. What is the difference Tunnel diode over other diode?
Compare with others, it exhibit very high speed and stable characteristic that is insensible to temperature.
104. What is PIN diode?
PIN diode is wider and intrinsic layer present between highly doped p-n layer. It exhibit the variable resistance characteristics based on the small changes in current value.
105. What is the application of PIN diode?
Switch.
Attenuator.
106. What is Schottky diode?
Schottky diode is a metal-semiconductor diode and the junction is between the metal and n type semiconductor. The purpose of Schottky diode is to improve the switching speed.
107. Show the comparison of forward voltage drop of diodes ?
For Si diode- 0.6V
For Ge diode-0.3V
For Schottky diode-0.1V.
108. What is the application of Schottky diode?
Clamping.
Discharge Protection in battery.
Rectifier.
Frequency mixing.
RF power detection.
109. What is Point contact diode?
Point contact diode is made up of semiconductor crystal. It’s a older version of Schottky diode.
110. What is the application of Point contact diode?
RF detection (AM Demodulation).
Rectification.
111. What is crystal diode?
Crystal diode is a type of point contact diode used for RF detection.
112. What is Step recovery diode?
The diode having ability to generate short pulse is called step recovery diode. During forward bias the value is 1 and reverse bias the value is 0.
113. What is the application of step recovery diode?
it is used in voltage multipliers.
114. What is Transient voltage suppression diode?
The diode which is used to protect against voltage spikes is called Transient voltage suppression diode.
115. What is constant current diode?
The diode which keeps the current constant even though voltage varies is called constant current diode. It is formed by using JFET, make a short circuit between gate and source and keep it as two terminal diode.
116. What is super barrier diode?
The diode which used as rectifier along with the surge handling ability.
117. What is surge?
It’s a short electrical wave .
118.Why do mirror reverse left and right?
mirror never do like that, human only think like that. e.g.
118.Why do mirror reverse left and right?
mirror never do like that, human only think like that. e.g.
119. How many types of wave?
Sine wave
Square wave
Triangular wave
Saw tooth wave
Step wave
Ramp wave
Impulse wave
Noise wave.
120. Draw sine, square, ramp, sawtooth and triangular wave?
121. draw impulse, step and noise wave?
When the device make a small AC signal input as a large AC signal, then it is called as amplifier.
143. How amplifier are classified?
Small signal amplifier
Large signal amplifier.
144. What is meant by small signal amplifier?
The amplifier which is designed to amplify a input signal having voltage level in (micro V) is called small signal amplifier.
eg. pre-amplifier, instrumentation amplifier.
145. What is meant by large signal amplifier?
The amplifier which is designed to amplify a large input signal or to switch heavy load current is called large signal amplifier.
eg. power amplifier, switching amplifier.
146. How to find the characteristic of Amplifier?
Based on the input impedance, output impedance and gain.
147. What is gain?
Gain is the ratio of output to the voltage.
if voltage gain, ratio of output voltage to the input voltage.
if power gain, ratio of output power to the input power.
148. What is the required characteristic for a good amplifier?
For a good amplifier required,
high input impedance,
high gain,
low output impedance.
149. What is Voltage amplifier?
if the output voltage is greater than input voltage and the voltage gain is increase is called voltage amplifier.
150. What is Power amplifier?
if the output power is greater than input power and voltage gain is zero, power gain is increase is called power amplifier.
151. Show the characteristics of common base?
fig b.input characteristics
fig c.output characteristic
.gif)
154. Which configuration is best and why?
CE configuration is best because of high voltage and current gain in its characteristics.
155. Give the comparison of all configuration in BJT?
common base having voltage gain and no current gain,
common emitter having voltage gain and current gain,
common collector having current gain and no voltage gain.
156. What is common base configuration?
In a BJT, the emitter base junction act as forward bias and collector base junction act as reverse bias. Base terminal is common for both input and output. so, it is called as common base configuration.
157. Why CB config having no current gain and show its voltage gain?
Because of the high emitter current current and low collector current, current gain is less than unity. It is represented by Alpha,
α= Ic/Ie
158. What is the application of CB configuration?
There is no phase shift between the input and output. so it is used as non-inverting amplifier and also used as a attenuator.
159.What is common emitter configuration?
In a BJT, the base emitter junction act as forward bias and collector emitter junction act as reverse bias. Emitter terminal is common for both input and output. so, it is called as common emitter configuration.
160. What is the current and voltage gain of CE conf?
According to kirchoff's current law,
Emitter current is the sum of the collector and base current. it having high current gain and minimum voltage gain. The collector gain is represented as beta,
β=Ic/Ib
161. Show relationship between Alpha and Beta?
162. What is the application of CE conf?
There is 180deg out of phase shift between the input and output. so it is used as inverting amplifier.
163. What is Common Collector Configuration?
The biasing is similar to CE but the input is given at the base and output is taken at the emitter. It is called emitter follower or Voltage follower.
164. Why no voltage gain and show the current gain of CC conf?
because of the output of emitter follows the base, no voltage gain. the current gain is given by,
165. What is the application of CC conf?
it is used for impedance matching and non inverting amplifier.
166. Comparison of CB,CE,CC conf?
167. Difference between npn and pnp?
the difference is given by
168. What is FET?
Field Effect Transistor(FET) is a three terminal unipolar transistor because of the current flow only by majority carrier. It is also called as voltage controlled transistor.
169. Why FET is called voltage controlled transistor?
The relationship between the input and output current depends on applied voltage between the gate. so it is called voltage controlled transistor.
170. Show the types of FET?
1.JFET(Junction Field Effect Transistor)
2.IGFET(Insulated Gate Field Effect Transistor) or MOSFET(Metal Oxide Semiconductor Field Effect Transistor).
171. Show the Structure of FET?
a.Structure of N type MOSFET
b.Structure of N type JFET
172. How JFET is classified and its symbol?
two types,
1.N channel JFET
2.P channel JFET.
173. How MOSFET is Classified and its symbol?
It is classified into two types,
1.N channel MOSFET
2.P channel MOSFET
Both types having two modes
1.Enhancement mode
2.Depletion mode.
174. Comparison of BJT, JFET, MOSFET terminals and its symbol?
175. Show the operation of JFET under zero bias for N channel JFET?
Because of holes and electron recombination, depletion region formed as shown in fig. The width of the depletion is less when no gate voltage is applied. so, the drain current is maximum.
176. Show the operation of JFET under bias for N channel JFET?
When some reverse bias voltage applied to gate, the the width of the depletion region increase. so there is no flow of current between drain and source at maximum reverse bias voltage of gate is called pinched off region.
185. What is MOSFET?
It is a unipolar transistor having insulator at the gate and having two modes of operation.
186. How many modes in MOSFET?
It having 2 modes,
1.Enhancement mode
2.Depletion mode
187.What is enhancement mode?
The mode which required some biasing voltage to make FET in ON position and vice versa is called enhancement mode.
188. What is depletion mode?
The mode which required some biasing voltage to make FET in OFF position and vice versa is called depletion mode.
189. How JFET operate in depletion mode?
It does not required any biasing voltage to make a FET in ON position. At 0v, FET in ON position.so, it operate in depletion mode.
190. Show the general classification of FET?
191. When the FET act as a switch in all modes?
192. Draw the structure of MOSFET?
impulse
step
noise
122. What is Transistor?
Transistor means transfer resistance. It is a three terminal semiconductor device which is used as a switch and amplifier.
123. How transistor are classified?
It is classified into two types based on the construction
1.Bipolar Transistor
a.PNP Transistor
b.NPN Transistor.
2.Unipolar Transistor
a.JFET
b.MOSFET.
124. What is BJT?
Bipolar Junction Transistor (BJT) is a bipolar transistor having current in it due to minority and majority carrier.
125. What is FET?
Field Effect Transistor (FET) is a unipolar transistor having current in it due to the majority carrier.
126. Which transistor speed is more?
BJT, because the current is high in it due to majority and minority carrier.
127. Draw the structure of BJT?
128. Show the symbol of BJT?
129. Define the layers in BJT?
it consist of three layer
the layer having moderate size and heavily doped is called Emitter,
the layer having small size and lightly doped is called base,
the layer having large size and moderately doped is called Collector.
130. Why BJT is current controlled device?
Because the output of the BJT is based on input base current.
131. Why FET is voltage controlled device?
Because the output of FET is based on applied gate voltage.
132. What are the configuration in BJT?
common base
common emitter
common collector.
133. Show the characteristics of BJT?
134. When a transistor act as switch?
During cut off region, transistor in Off state,
During saturation region, transistor in On state.
135. How to make a switch using transistor?
By applying pulse wave using timer circuit(IC555), we can make a transistor as a switch by applying pulse.
136. Show the condition in cut off region?
137. Show the condition of saturation region?
138. When the BJT in closed circuit?
when the base emitter voltage is greater than 0.6 then the transistor in closed path.
139. When transistor act as amplifier?
During Active region at Q-point the transistor act as amplifier.
140. What is meant by Q-point?
Q-point or Quiescent point is a DC supply for transistor to make it as a amplifier. when we apply any AC signal, then amplification takes place. When the transistor in Q-point, it wont jump to saturation or cut off region.
141. How to find the characteristics of amplifier?
Based on the transistor factor (Beta). Beta is the ratio of collector current to the base current.
142. What is amplifier?
When the device make a small AC signal input as a large AC signal, then it is called as amplifier.
143. How amplifier are classified?
Small signal amplifier
Large signal amplifier.
144. What is meant by small signal amplifier?
The amplifier which is designed to amplify a input signal having voltage level in (micro V) is called small signal amplifier.
eg. pre-amplifier, instrumentation amplifier.
145. What is meant by large signal amplifier?
The amplifier which is designed to amplify a large input signal or to switch heavy load current is called large signal amplifier.
eg. power amplifier, switching amplifier.
146. How to find the characteristic of Amplifier?
Based on the input impedance, output impedance and gain.
147. What is gain?
Gain is the ratio of output to the voltage.
if voltage gain, ratio of output voltage to the input voltage.
if power gain, ratio of output power to the input power.
148. What is the required characteristic for a good amplifier?
For a good amplifier required,
high input impedance,
high gain,
low output impedance.
149. What is Voltage amplifier?
if the output voltage is greater than input voltage and the voltage gain is increase is called voltage amplifier.
150. What is Power amplifier?
if the output power is greater than input power and voltage gain is zero, power gain is increase is called power amplifier.
151. Show the characteristics of common base?
fig b.input characteristics
fig c.output characteristic
152. Show the characteristics of common emitter?
fig a.input characteristics
fig b.output characteristic
153. Show the characteristics of common collector?
fig b.input characteristics
fig c.output characteristic
154. Which configuration is best and why?
CE configuration is best because of high voltage and current gain in its characteristics.
155. Give the comparison of all configuration in BJT?
common base having voltage gain and no current gain,
common emitter having voltage gain and current gain,
common collector having current gain and no voltage gain.
156. What is common base configuration?
In a BJT, the emitter base junction act as forward bias and collector base junction act as reverse bias. Base terminal is common for both input and output. so, it is called as common base configuration.
157. Why CB config having no current gain and show its voltage gain?
Because of the high emitter current current and low collector current, current gain is less than unity. It is represented by Alpha,
α= Ic/Ie
There is no phase shift between the input and output. so it is used as non-inverting amplifier and also used as a attenuator.
159.What is common emitter configuration?
In a BJT, the base emitter junction act as forward bias and collector emitter junction act as reverse bias. Emitter terminal is common for both input and output. so, it is called as common emitter configuration.
160. What is the current and voltage gain of CE conf?
According to kirchoff's current law,
Emitter current is the sum of the collector and base current. it having high current gain and minimum voltage gain. The collector gain is represented as beta,
β=Ic/Ib
161. Show relationship between Alpha and Beta?
162. What is the application of CE conf?
There is 180deg out of phase shift between the input and output. so it is used as inverting amplifier.
163. What is Common Collector Configuration?
The biasing is similar to CE but the input is given at the base and output is taken at the emitter. It is called emitter follower or Voltage follower.
164. Why no voltage gain and show the current gain of CC conf?
because of the output of emitter follows the base, no voltage gain. the current gain is given by,
165. What is the application of CC conf?
it is used for impedance matching and non inverting amplifier.
166. Comparison of CB,CE,CC conf?
| Characteristic | Common Base | Common Emitter | Common Collector |
| Input Impedance | Low | Medium | High |
| Output Impedance | Very High | High | Low |
| Phase Angle | 0o | 180o | 0o |
| Voltage Gain | High | Medium | Low |
| Current Gain | Low | Medium | High |
| Power Gain | Low | Very High | Medium |
167. Difference between npn and pnp?
the difference is given by
| Between Transistor Terminals | PNP | NPN | |
| Collector | Emitter | RHIGH | RHIGH |
| Collector | Base | RLOW | RHIGH |
| Emitter | Collector | RHIGH | RHIGH |
| Emitter | Base | RLOW | RHIGH |
| Base | Collector | RHIGH | RLOW |
| Base | Emitter | RHIGH | RLOW |
| Applied voltages | B-E Junction Bias (NPN) | B-C Junction Bias (NPN) | Mode (NPN) |
|---|---|---|---|
| E < B < C | Forward | Reverse | Forward active |
| E < B > C | Forward | Forward | Saturation |
| E > B < C | Reverse | Reverse | Cut-off |
| E > B > C | Reverse | Forward | Reverse-active |
| Applied voltages | B-E Junction Bias (PNP) | B-C Junction Bias (PNP) | Mode (PNP) |
| E < B < C | Reverse | Forward | Reverse-active |
| E < B > C | Reverse | Reverse | Cut-off |
| E > B < C | Forward | Forward | Saturation |
| E > B > C | Forward | Reverse | Forward active |
168. What is FET?
Field Effect Transistor(FET) is a three terminal unipolar transistor because of the current flow only by majority carrier. It is also called as voltage controlled transistor.
169. Why FET is called voltage controlled transistor?
The relationship between the input and output current depends on applied voltage between the gate. so it is called voltage controlled transistor.
170. Show the types of FET?
1.JFET(Junction Field Effect Transistor)
2.IGFET(Insulated Gate Field Effect Transistor) or MOSFET(Metal Oxide Semiconductor Field Effect Transistor).
171. Show the Structure of FET?
a.Structure of N type MOSFET
b.Structure of N type JFET
172. How JFET is classified and its symbol?
two types,
1.N channel JFET
2.P channel JFET.
173. How MOSFET is Classified and its symbol?
It is classified into two types,
1.N channel MOSFET
2.P channel MOSFET
Both types having two modes
1.Enhancement mode
2.Depletion mode.
174. Comparison of BJT, JFET, MOSFET terminals and its symbol?
175. Show the operation of JFET under zero bias for N channel JFET?
Because of holes and electron recombination, depletion region formed as shown in fig. The width of the depletion is less when no gate voltage is applied. so, the drain current is maximum.
When some reverse bias voltage applied to gate, the the width of the depletion region increase. so there is no flow of current between drain and source at maximum reverse bias voltage of gate is called pinched off region.
177. Show the characteristics of JFET?
Based on the gate voltage, it consist of four region
1.Pinch off region
2.Ohmic region
3.Saturation region
4.Break down region.
178. What is ohmic region?
When the gate voltage is zero, then the JFET act as a Voltage controlled resistor.
179. What is saturation or active region?
The region in which JFET is controlled by using applied gate voltage. drain current is given by,
IDSS-maximum drain current,
VGS =voltage between gate and source,
VP= pinch off voltage.
180. What is Breakdown region?
The region at which the drain current flowing through the channel is more than the maximum drain current because of the breakage of depletion region and the gate voltage cannot control the drain current.
181. How to calculate the gain of JFET?
The gain is mentioned here as transconductance . The ratio of changing voltage to the changing current is called as transconductance.
182. Show JFET as an amplifier structure?
R1,R2 act as a voltage divider which is used to apply correct input to gate and also used to set Q point.
183.Explain P channel JFET?
All the things which discussed for N channel JFET is similar to P channel JFET but need to apply opposite polarity power supply. The drain current decrease with increase in gate voltage.
184. Advantage of FET over BJT?
1.Temperature affect BJT not FET.
2.FET having high input impedance.
3.FET having low power consumption.
When the gate voltage is zero, then the JFET act as a Voltage controlled resistor.
179. What is saturation or active region?
The region in which JFET is controlled by using applied gate voltage. drain current is given by,
IDSS-maximum drain current,
VGS =voltage between gate and source,
VP= pinch off voltage.
180. What is Breakdown region?
The region at which the drain current flowing through the channel is more than the maximum drain current because of the breakage of depletion region and the gate voltage cannot control the drain current.
181. How to calculate the gain of JFET?
The gain is mentioned here as transconductance . The ratio of changing voltage to the changing current is called as transconductance.
182. Show JFET as an amplifier structure?
R1,R2 act as a voltage divider which is used to apply correct input to gate and also used to set Q point.
183.Explain P channel JFET?
184. Advantage of FET over BJT?
1.Temperature affect BJT not FET.
2.FET having high input impedance.
3.FET having low power consumption.
It is a unipolar transistor having insulator at the gate and having two modes of operation.
186. How many modes in MOSFET?
It having 2 modes,
1.Enhancement mode
2.Depletion mode
187.What is enhancement mode?
The mode which required some biasing voltage to make FET in ON position and vice versa is called enhancement mode.
188. What is depletion mode?
The mode which required some biasing voltage to make FET in OFF position and vice versa is called depletion mode.
189. How JFET operate in depletion mode?
It does not required any biasing voltage to make a FET in ON position. At 0v, FET in ON position.so, it operate in depletion mode.
190. Show the general classification of FET?
191. When the FET act as a switch in all modes?
| Junction FET | Metal Oxide Semiconductor FET | |||||
| Type | Depletion Mode | Depletion Mode | Enhancement Mode | |||
| Bias | ON | OFF | ON | OFF | ON | OFF |
| N-channel | 0v | -ve | 0v | -ve | +ve | 0v |
| P-channel | 0v | +ve | 0v | +ve | -ve | 0v |
192. Draw the structure of MOSFET?
Digital Electronics Q&A
1.What is digital system?
Systems which process discrete values and digital values are called digital systems.
All discrete signals are digital signals but not all digital signals are discrete signals
.jpg) |
| Discrete signal |
.jpg) |
| Digital Signal |
2.What is analog system?
Systems which are capable of processing a continuous range of values varying with respect to time are called analog systems.
3.Difference between analog signal and digital signal.
.gif) |
| Analog voltage vs time |
 |
| Digital voltage vs time |
Analog=continuous
Digital=Discrete(step by step)
4.Example for analog and digital system.
|
Analog watch and digital watch.
.jpg)
5. what are the advantages of digital system?
Exact value of voltage or current are not important.
Information storage is easy.
Accuracy and precision are greater.
Digital circuits are less affected by noise.
More digital circuitry can be fabricated on IC chips.
LOGIC GATES
6.What is logic gates?
A logic gate is an electronic circuit/device which makes the logical decisions(0 or 1). Logic gates have one or more inputs and only one output.
7.What are the most common logic gates?
OR(addition),AND(multiplication),NOT(inversion),NOR(inverse of OR),NAND(inverse of AND)
8.What are the universal gates? and Why?
NOR and NAND.All gates can be implemented by using universal gates.
9.Write are the symbols used for logic gates?
 |
| NOT |
 |
| AND |
 |
| OR |
 |
| NAND |
 |
| NOR |
10.What are the development stages of logic gates?
DRL(Diode-Resistor logic )->TTL (Transistor-Transistor logic)->CMOS(Complementary metal oxide semiconductor)
 |
| DRL |
 |
| TTL |
 |
| CMOS |
Fig. 2-input NAND gate
11.State Moore’s law?
"The number of transistors and resistors on a single chip will double every 18 months"
Communication Q&A
1. What is communication?
Transfer information from source to destination is called communication.
2. How communication are classified?
Based on the medium,
1. Wired communication
2. Wireless communication
Based on the techniques,
1. Analog communication
2. Digital communication
Based on the mode,
1. Serial communication
2. Parallel communication.
3.block diagram of communication system ?
communication system are designed to send (message or information) from a source to one or more destination.
general block diagram of communication system :-
4.what are the basic parts of communication systems?
The heart of the communication system consists of three basic parts.
They are
- The transmitter
- The channel and
- The receiver
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