# Electronic Devices and Circuits Questions and Answers – The Insulated-Gate FET(MOSFET) – 1

This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “The Insulated-Gate FET(MOSFET) – 1”.

1. Which of the following is true about MOSFET?
a) There is no direction between channel and gate terminal
b) There exists a channel and gate short connection
c) Channel is not present and cannot be created
d) They have low input impedance

Explanation: According to the physical structure of MOSFET, there is a Silicon dioxide layer between channel and gate terminal. Since Silicon dioxide acts as a resistor with infinite resistance, there is no connection between the channel and gate terminal of MOSFET.

2. What will happen if a metal is used instead of Silicon dioxide in the fabrication of MOSFET?
a) Device burns
b) No changes in the behaviour of MOSFET
c) Input impedance increases
d) Current cannot be generated in MOSFET

Explanation: If a metal is used instead of Silicon dioxide, once the biasing condition is achieved, as the drain to source voltage current starts floating to gate terminal resulting in burning of the device.

3. Necessary condition to create a channel in n-channel enhancement MOSFET is ____________
a) Vgs > Vt
b) Vgs < Vt
c) Vgs < 2Vt
d) 2Vgs > Vt

Explanation: When gate to source voltage exceeds the threshold voltage, the source and substrate and drain and substrate forms a forward bias resulting in the formation of depletion region which acts as a channel.

4. Determine the least voltage VDS required to operate E-MOSFET on active region. (Vgs=2V,Vt=0.7V)
a) 1.2V
b) 2V
c) 0V
d) 1.3V

Explanation: VDS=Vgs-Vt VDS=2-0.7V VDS=1.3V.

5. Determine the value of K (System constructor constant) for a MOSFET with Vgs=8V,Vt=2V and ID=10A?
a) 0.001A/v2
b) 0.278 A/v2
c) 0.5761A/v2
d) 0.0021A/v2

Explanation: K=ID/(Vgs-Vt)2
K=10/36
K=0.278.

6. Which of the following is the necessary to hold drain current in 0 for n channel E-MOSFET?
a) Vgs > Vt
b) Vgs < Vt
c) Vgs < 2Vt
d) 2Vgs > Vt

Explanation: For Vgs < Vt, the channel is not created and hence there will be no electron flow from source to drain. Therefore the drain current will be zero.

7. Which of the following is the necessary to hold drain current in 0 for p channel E-MOSFET?
a) Vgs > Vt
b) Vgs < Vt
c) Vgs < 2Vt
d) 2Vgs > Vt

Explanation: For Vgs > Vt, both of the drain-substrate and source-substrate will be reverse biased and hence the depletion region is narrower. Hence the channel is not created and hence there will be no electron flow from source to drain. Therefore the drain current will be zero.

8. In a p-channel E-MOSFET, the current becomes constant in saturation region. Which of the following condition depicts this?
a) VDS = 2Vgs-Vt
b) VDS > Vgs-Vt
c) VDS ≤ Vgs-Vt
d) VDS = Vgs

Explanation: The p-channel E-MOSFET operates in the saturation region when VDS > Vgs-Vt, since we will be fixing the gate to source voltage and threshold is a system constant, whatever may be the value of VDS which is lesser than Vgs-Vt, the current remains the same.

9. In an n-channel E-MOSFET, the current becomes constant in saturation region. Which of the following condition depicts this?
a) VDS = 2Vgs-Vt
b) VDS > Vgs-Vt
c) VDS ≤ Vgs-Vt
d) VDS = Vgs

Explanation: The n-channel E-MOSFET operates in the saturation region when VDS > Vgs-Vt, since we will be fixing the gate to source voltage and threshold is a system constant, whatever may be the value of VDS which is greater than Vgs-Vt, the current remains the same.

10. Which of the following is true about n-channel E-MOSFET?
a) Electrons are the majority charge carries
b) Holes are the majority charge carries
c) Both holes and electrons are present in same ratio
d) Neutrons are the charge carriers

Explanation: n-channel E-MOSFET is designed in such a way that the source and drain are formed by the n-type impurity which contains electrons as the majority charge carriers. The doping concentration of source and drain is slightly more than the gate and body, and thus the channel created is by electrons of a source and drain.

Sanfoundry Global Education & Learning Series – Electronic Devices and Circuits.

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