Semiconductor Electronics

The collector current in a common base amplifier using n-p-n transistor is 24 mA. If 80% of the electrons released by the emitter is accepted by the collector, then the base current is numerically :

1. 3 mA and entering the base
2. 6 mA and leaving the base
3. 3 mA and leaving the base
4. 6 mA and entering the base

For transistor action, which of the following statements is correct?

1. Base, emitter and collector regions should have same size.
2. Both emitter junction as well as the collector junction are forward biased.
3. The base region must be very thin and lightly doped.
4. Base, emitter and collector regions should have same doping concentrations.

In the circuit shown in the figure, the input voltage Vi is 20 V, VBE = 0 and VCE = 0. The values of IB, IC and β are given by [figure]

1. IB = 40 , IC = 10 mA, β = 250
2. IB = 25 , IC = 5 mA, β = 200
3. IB = 20 , IC = 5 mA, β = 250
4. IB = 40 , IC = 5 mA, β = 125

In a common emitter transistor amplifier the audio signal voltage across the collector is 3 V. The resistance of collector is 3 k . If current gain is 100 and the base resistance is 2 k , the voltage and power gain of the amplifier is

1. 15 and 200
2. 150 and 15000
3. 20 and 2000
4. 200 and 1000

A npn transistor is connected in common emitter configuration in a given amplifier. A load resistance of 800 is connected in the collector circuit and the voltage drop across it is 0.8 V. If the current amplification factor is 0.96 and the input resistance of the circuit is 192 , the voltage gain and the power gain of the amplifier will respectively be

1. 4, 4
2. 4, 3.69
3. 4, 3.84
4. 3.69, 3.84

For CE transistor amplifier, the audio signal voltage across the collector resistance of 2 k is 4 V. If the current amplification factor of the transistor is 100 and the base resistance is 1 k , then the input signal voltage is

1. 10 mV
2. 20 mV
3. 30 mV
4. 15 mV

The input signal given to a CE amplifier having a voltage gain of 150 is Vi = 2 (15t + 3 ). The corresponding output signal will be

1. 2 (15t + 5 6 )
2. 300 (15t + 4 3 )
3. 300 (15t + 3 )
4. 75 (15t + 2 3 )

In a common emitter (CE) amplifier having a voltage gain G, the transistor used has transconductance 0.03 mho and current gain 25. If the above transistor is replaced with another one with transconductance 0.02 mho and current gain 20, the voltage gain will be

1. 13G
2. 54G
3. 23G
4. 1.5G

One way in which the operation of an n-p-n transistor differs from that of a p-n-p is

1. The emitter junction injects minority carriers into the base region of the p-n-p
2. The emitter injects holes into the base of the p-n-p and electrons into the base region of n-p-n
3. The emitter injects holes into the base of n-p-n
4. The emitter junction is reverse biased in n-p-n

The input resistance of a silicon transistor is 100 . Base current is changed by 40 which results in a change in collector current by 2 mA. This transistor is used as a common emitter amplifier with a load resistance of 4 k . The voltage gain of the amplifier is

1. 2000
2. 3000
3. 4000
4. 1000

In a CE transistor amplifier, the audio signal voltage across the collector resistance of 2 k is 2 V. If the base resistance is 1 k and the current amplification of the transistor is 100, the input signal voltage is

1. 0.1 V
2. 1.0 V
3. 1 mV
4. 10 mV

Transfer characteristics [output voltage (V0) vs input voltage (Vi)] for a base biased transistor in CE configuration is as shown in the figure. For using transistor as a switch, it is used [figure]

1. in region III
2. both in region (I) and (III)
3. in region II
4. in region I

A transistor is operated in common emitter configuration at VC = 2 V such that a change in the base current from 100 A to 300 A produces a change in the collector current from 10 mA to 20 mA. The current gain is

1. 50
2. 75
3. 100
4. 25

For transistor action Which one of the following pairs of statements is correct?

1. D and A
2. A and B
3. B and C
4. C and D

A common emitter amplifier has a voltage gain of 50, an input impedance of 100 and an output impedance of 200 . The power gain of the amplifier is

1. 500
2. 1000
3. 1250
4. 50

A transistor is operated in common-emitter configuration at VC = 2 V such that a change in the base current from 100 to 200 produces a change in the collector current from 5 mA to 10 mA. The current gain is

1. 100
2. 150
3. 50
4. 75

The voltage gain of an amplifier with 9% negative feedback is 10. The voltage gain without feedback will be

1. 1.25
2. 100
3. 90
4. 10

A transistor is operated in common emitter configuration at constant collector voltage VC = 1.5 V such that a change in the base current from 100 to 150 produces a change in the collector current from 5 mA to 10 mA. The current gain is

1. 50
2. 67
3. 75
4. 100

An n-p-n transistor conducts when

1. both collector and emitter are positive with respect to the base
2. collector is positive and emitter is negative with respect to the base
3. collector is positive and emitter is at same potential as the base
4. both collector and emitter are negative with respect to the base

For a transistor ICIE = 0.96, then current gain for common emitter is

1. 12
2. 6
3. 48
4. 24

For a common base circuit if ICIE = 0.98 then current gain for common emitter circuit will be

1. 49
2. 98
3. 4.9
4. 25.5

The correct relation between and for a transistor is

1. = 1-
2. = 1-
3. = -1
4. = 1