Physics : Semiconductor Electronics: Materials, Devices and Simple Circuits

Which one of the following statement is false?

• Pure Si doped with trivalent impurities given a p- type semiconductor

• Majority carriers in a p- type semiconductor are holes

• Minority carriers in a p- type semiconductor are electron

• Minority carriers in a p- type semiconductor are electron

The device that can act as a complete electronic circuit is

• Junction diode

• Integrated circuit

• Junction transistor

• Junction transistor

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

• 500

• 1000

• 1250

• 1250

To get an output Y = 1 from the circuit shown below, the input must be

• A	B	C
  0	1	0

• A	B	C
  0	0	1

• A	B	C
  1	0	1

• A	B	C
  1	0	1

For transistor action

A) Base, emitter and collector regions should have similar size and doping concentrations.

B) The base region must be very thin and lightly doped.

C) The emitter-base junction is forward biased and base -collector junction is reverse biased

D) Both the emitter-base junction as well as the base-collector junction are forward biased.

• (D) and (A)

• (A) and (B)

• (B) and (C)

• (B) and (C)

The following figure shows a logic gate circuit with two inputs A and B the output Y. The voltage waveforms of A, B and Y are as given


The logic gate is

•  NOR gate

• OR Gate

• AND gate

• AND gate

A p-n photodiode is fabricated from a semiconductor with a band gap of 2.5 eV. It ca detect a signal of wavelength

• 6000 A^o

• 4000 nm

• 6000 nm

• 6000 nm

If a diamagnetic substance is brought near the north or the south pole of a bar magnet, it is 

• repelled by both the poles

• repelled by the north pole and attracted by the south pole

• attracted by the north pole and repelled by the south  pole

• attracted by the north pole and repelled by the south  pole

The symbolic representation of four logic gates


The logic symbols for OR, NOT and NAND gates are respectively

• (iii), (iv), (ii)

• (iv), (i), (iii)

• (iv), (ii), (i)

• (iv), (ii), (i)

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

• 75

• 100

• 150

• 150