Semiconductor Electronics · Question 21

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

Consider the following statements (A) and (B) and identify the correct answer. (A) A Zener diode is connected in reverse bias, when used as a voltage regulator. (B) The potential barrier of p-n junction lies between 0.1 V to 0.3 V.

1. (A) is incorrect but (B) is correct.
2. (A) and (B) both are correct.
3. (A) and (B) both are incorrect.
4. (A) is correct and (B) is incorrect.

The electron concentration in an n-type semiconductor is the same as hole concentration in a p-type semiconductor. An external field (electric) is applied across each of them. Compare the currents in them.

1. No current will flow in p-type, current will only flow in n-type
2. Current in n-type = current in p-type
3. current in p-type > current in n-type
4. current in n-type > current in p-type

For the given circuit, the input digital signals are applied at the terminals A, B and C. What would be the output at the terminal y? [figure]

1. [figure]
2. [figure]
3. [figure]
4. [figure]

The increase in the width of the depletion region in a p-n junction diode is due to :

1. reverse bias only
2. both forward bias and reverse bias
3. increase in forward current
4. forward bias only

For the logic circuit shown, the truth table is : [figure]

1. [figure]
2. [figure]
3. [figure]
4. [figure]

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.

The correct Boolean operation represented by the circuit diagram drawn is : [figure]

1. OR
2. NAND
3. NOR
4. AND

For a p-type semiconductor, which of the following statements is true?

1. Holes are the majority carriers and trivalent atoms are the dopants.
2. Holes are the majority carriers and pentavalent atoms are the dopants.
3. Electrons are the majority carriers and pentavalent atoms are the dopants.
4. Electrons are the majority carriers and trivalent atoms are the dopants.

In the combination of the following gates the output Y can be written in terms of inputs A and B as [figure]

1. A.B
2. A. B + A.B
3. A. B + A.B
4. A + B