# FACTS Questions and Answers – Diode PN Junction & Transistor – Set 3

This set of FACTS Multiple Choice Questions & Answers (MCQs) focuses on “Diode PN Junction & Transistor – Set 3”.

1. ________ is a measure of voltage transients of a diode undergoing reverse recovery.
a) V Factor
b) S Factor
c) H Factor
d) I Factor

Explanation: S Factor is a measure of voltage transients of a diode undergoing reverse recovery. S factor means Softness Factor. It helps to get an idea if the given diode has high voltage transient or low voltage transient.

2. If trr = ta + tb, S factor is given by ________
a) ta + tb
b) tb – ta
c) tb / ta
d) tb * ta

Explanation: If trr = ta + tb, S factor is given by tb / ta. The value of S is either less than or equal to one. The value of S is not greater than one.

3. In pn junction diode, the anode is kept positive with respect to the cathode for forward conduction.
a) True
b) False

Explanation: In the pn junction diode, the anode is kept positive with respect to the cathode for forward conduction. It is then said to be in forward biased condition. In the pn junction diode, when the cathode is kept positive with respect to the anode, it is reversed biased.

4. Doping a semiconductor with impurities can alter its conduction characteristics.
a) True
b) False

Explanation: Doping a semiconductor with impurities can alter its conduction characteristics. Generally intrinsic semiconductors are doped with impurities. The resultant semiconductors are called extrinsic ones.

5. With doping, the number of carriers in a semiconductor substrate ________
a) is increased
b) is increased
c) remains same
d) cannot be known

Explanation: With doping, the number of carriers in a semiconductor is increased. Actually carriers are nothing but electron hole pairs. Doping with the specific group elements, the semiconductors become either p-type of n-type.

6. FETs are bipolar transistors.
a) True
b) False

Explanation: FETs are Not bipolar, but unipolar transistors. ‘Uni’ means ‘one’ and FETs involve single type of carrier during operation i.e., either electrons or holes. A FET does not use both electrons or holes as charge carriers in its operation.

7. Both diode and FETs are only minority carriers.
a) True
b) False

Explanation: The given statement is false. This is because diodes generally possess both majority and minority carriers and they both can contribute to the operation of diodes as per the required functionality and design. Again FETs use either majority carriers (pre-dominant) or minority carriers in their mechanism.

8. Because of doping a semiconductor, its withstand voltage decreases.
a) True
b) False

Explanation: Because of doping a semiconductor, its withstand voltage at the junction decreases. But on doing so its current capability increases due to increased generation of electron-hole pairs. Lower doping indicates higher voltage capability and lower current capability.

9. Diode provides an active channel in its structure for its charge carriers to flow through it.
a) True
b) False

Explanation: It is FET not diode that provides an active channel in its structure for its charge carriers to flow through it. The charge carriers – electrons or holes flow through this channel from the source to the drain of the FET. Ohmic contacts do connect these source and drain terminal conductors to the semiconductor.

10. The conductivity of the channel in FET is NOT a function of the potential applied across its gate and source terminals.
a) True
b) False

Explanation: The conductivity of the channel in FET is NOT a function of the potential applied across its gate and source terminals. Irrespective of p-type or n-type channel of the given FET, this relation holds good for every FET.

11. In FETs, the drain and source terminals are always doped of opposite type to that of the channel.
a) True
b) False

Explanation: In FETs, the drain and source terminals are NOT always doped of opposite type to that of the channel. In enhancement-type FETs, the drain and source terminals may be doped of opposite type to that of the channel. Again in depletion-type FETs, the drain and source terminals may be doped of similar type as that to the channel.

12. DGMOSFET stands for ________
a) dual-gate MOSFET
b) direct-gate MOSFET
c) diffused-gate MOSFET
d) drain-gate MOSFET

Explanation: DGMOSFET stands dual-gate MOSFET. MOSFET generally employs SiO2 as an insulator between the gate and the body. When the configuration comes with two insulated gates, it forms DGMOSFET.

13. FET operates using an electric field effect to make charges channelize through a semiconductor channel.
a) True
b) False

Explanation: FET operates using an electric field effect to make charges channelize through a semiconductor channel. The control of flow of carriers is achieved through the gate terminal. With its placement in very close proximity to the channel, its electric charge is able to affect the channel.

14. FET is voltage controlled element.
a) True
b) False

Explanation: FET is voltage controlled or voltage operated element. This is because the current flowing in the channel of an FET is controlled by the electric field with the help of its gate terminal.

15. JFET can be of enhancement mode type.
a) True
b) False

Explanation: JFET cannot be of enhancement mode type. JFET can be of depletion mode type. However, JFET can be either p-channel or n-channel.

Sanfoundry Global Education & Learning Series – Flexible AC Transmission System (FACTS).

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