Physics : Semiconductor Electronics: Materials, Devices and Simple Circuits

In a transistor circuit, the base current changes from 30 µA to 90 µA. If the current gain of the transistor is 30%, the change in the collector current is

• 4 mA

• 2 mA

• 3.5 mA

• 1.8 mA

In a full wave rectifier, input AC current has a frequency v. The output frequency of current is

• $\frac{\mathrm{v}}{2}$

• v

• 2 v

• None of these

A full wave rectifier circuit along with the output is shown in the figure. The contribution (s) from the diode 1 is ( are )

• C

• A , C

• B , D

• A, B , C , D

Two identical p-n junctions may be connected in series with a battery in three ways as shown in the figure.

The potential drops across the two n-p junctions are equal in

• circuit 1 and circuit 2

• circuit 2 and circuit 3

• circuit 3 and circuit 1

• circuit 1 only

A transistor is used in common emitter mode as an  amplifier, then

• the base emitter junction is forward unbiased

• the base emitter junction is reverse biased

• the input signal is connected in series with the voltage applied to bias of the base emitter junction

• the input signal is connected in series with the voltage applied to bias the emitter collector junction

A transistor is connected in CE configuration. The supply to the collector is 8 V and the voltage drop across a resistor of 400 Ω in the collector circuit is 0.5 V. If the current gain factor is $\mathrm{\alpha }$ = 0.96 then, the base current will be nearly

• 52 µA

• 42 µA

• 32 µA

• 26 µA

The width of depletion layer in a p-n junction diode

• increases when a forward bias is applied

• increases when a reverse bias is applied

• decreases when a reverse bias is applied

• remains same irrespective of bias voltage

Which of the following truth table is of NAND gate ?

To get an output y = 1 from the circuit shown the inputs A, B and C must be respectively.

• 0, 1, 0

• 1, 0, 0

• 1, 0, 1

• 1, 1, 0

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 mhoand current gain 20,  the voltage gain will be

• $\frac{5}{4}\mathrm{G}$

• $\frac{2}{3}\mathrm{G}$

• 1.5 G

• $\frac{1}{3}\mathrm{G}$