Mechatronics Questions and Answers – Solid State Electronic Devices – Field Effect Transistor

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This set of Mechatronics Multiple Choice Questions & Answers (MCQs) focuses on “Solid State Electronic Devices – Field Effect Transistor”.

1. Which is the majority charge carrier in N-channel JFET?
a) Electrons
b) Negative ions
c) Holes
d) Positive ions
View Answer

Answer: a
Explanation: Electrons are the majority charge carrier in N-channel JFET. The channel formed is in between source and drain which are made of p-type semiconductor material. For conduction between source and drain, a potential difference is created across the gate terminal which forms a n-channel between source and drain.
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2. Which type of channel is formed, between P-type source, N-type substrate and P-type drain terminal, when a positive voltage is applied on the gate terminal of an enhancement type MOSFET?
a) P-channel
b) N-channel
c) No channel
d) Half N channel half P channel
View Answer

Answer: b
Explanation: N-channel is formed, between P-type source, N-type substrate and P-type drain terminal, when a positive voltage is applied on the gate terminal of an enhancement type MOSFET. When the positive voltage is applied on the gate terminal, it attracts all the electrons from the N-type substrate and forms a N-channel between source and drain.

3. What are the three terminals of JFET?
a) Source, Drain and Base
b) Emitter, Base and Collector
c) Source, Drain and Gate
d) Emitter, Base and Drain
View Answer

Answer: c
Explanation: The three terminals of JFET are Source, Drain and Gate. The P-channel JFET has a heavily doped gate of N-type and lightly doped channel of p-type. The N-channel JFET has heavily doped gate of P-type and lightly doped channel of N-type.

4. How many terminals does a MOSFET have?
a) Two
b) Three
c) Four
d) Five
View Answer

Answer: c
Explanation: MOSFET has four terminals. These terminals are namely Source, drain, gate and substrate. The source and drain are heavily doped which can be either of P-type or N-type material and the substrate in lightly doped of either N-type or P-type material respectively.

5. When a negative voltage is applied on the gate terminal, a N channel is formed between N-type source, P-type substrate and N-type drain terminal of an enhancement type MOSFET.
a) True
b) False
View Answer

Answer: b
Explanation: When a negative voltage is applied on the gate terminal, a P channel is formed between N-type source, P-type substrate and N-type drain terminal. When the negative voltage is applied on the gate terminal, it attracts all the holes from the P-type substrate and forms a p-channel between source and drain.
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6. Enhancement and depletion type are the two types of metal oxide semiconductor field effect transistor.
a) True
b) False
View Answer

Answer: a
Explanation: Enhancement and depletion type are the two types of metal oxide semiconductor field effect transistor. In enhancement type MOSFET no prior channel is inbuilt; a voltage must be applied so as to build the channel. In depletion type MOSFET a channel is already built, even without applying any external voltage.

7. MOSFET stands for ____
a) Metal Oxidized Semiconductor Field Effect Transistor
b) Metal Oxide Semiconductor Field Effect Transistor
c) Metallic Oxidized Semiconductor Field Effect Transistor
d) Metal Oxide Superconductor Field Effect Transistor
View Answer

Answer: b
Explanation: MOSFET stands for “Metal Oxide Semiconductor Field Effect Transistor”. It is a type of Field Effect Transistor (FET) that has a insulated gate for which it is also called as insulated gate field effect transistor. The voltage of the gate determines the electrical conductivity of the device.

8. IRF9540N 8mm in an example of which type of transistor?
a) Junction field effect transistor
b) Bipolar junction transistor
c) Metal oxide field effect transistor
d) NPN transistor
View Answer

Answer: c
Explanation: IRF9540N 8mm in an example of Metal oxide field effect transistor(MOSFET). It has very fast switching speed and works on advanced techniques to achieve very low resistance per silicon area.

9. Field effect transistor is a _______ controlled device.
a) Current
b) Inductance
c) Voltage
d) Resistance
View Answer

Answer: c
Explanation: Field effect transistor (FET) is a voltage controlled device. It is so because the output characteristics of these transistors depend on the field and the filed generated depends on the voltage. Where as bipolar junction transistors is a current control device.
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10. Which is the majority charge carrier in P-channel JFET?
a) Electrons
b) Negative ions
c) Holes
d) Positive ions
View Answer

Answer: c
Explanation: Holes are the majority charge carrier in P-channel JFET. The channel formed is in between source and drain which are made of n-type semiconductor material. For conduction between source and drain, a potential difference is created across the gate terminal which forms a p-channel between source and drain.

11. What is the transconductance of an n-channel JFET (Junction Field effect transistor) if its gate to source voltage is -3Volts, pinch-off voltage is -1 volts and no bias drain current is 2miliAmpere?
a) 2mA/V
b) 6mA/V
c) 4mA/V
d) 8mA/V
View Answer

Answer: d
Explanation: Given:
Gate to source voltage(Vgs)=-3Volts
Pinch-off voltage(Vp)=-1 volts
No bias drain current(Idss)=2mA
Transconductance(gm)={(2*Idss)/Vp)}*{1-(Vgs/Vp)}
Transconductance(gm)={(2*2mA)/-1V)}*{1-(-3V/-1 V)}=>8mA/V

12. What will be the transconductance of an n-channel JFET (Junction Field effect transistor) if Gate to source voltage(Vgs) is equal to Pinch-off voltage(Vp)?
a) 1mA/V
b) 0mA/V
c) -1mA/V
d) 2mA/V
View Answer

Answer: b
Explanation: Given:
Gate to source voltage(Vgs) = Pinch-off voltage(Vp)
Transconductance(gm)={(2*Idss)/Vp)}*{1-(Vgs/Vp)}
Transconductance(gm)={(2*Idss)/Vp)}*{1-(1)} [Since Vgs = Vp] Transconductance(gm)=0 mA/V

13. What is the no bias drain to source current of an n-channel JFET (Junction Field effect transistor) if its gate to source voltage is -2Volts, pinch-off voltage is -1 volts and transconductance is 2mA/V?
a) 1mA/V
b) 6mA/V
c) 2mA/V
d) 1mA
View Answer

Answer: d
Explanation: Given:
Gate to source voltage(Vgs) = -2Volts
Pinch-off voltage(Vp) = -1 volts
Transconductance = 2mA/V
Transconductance(gm) = {(2*Idss)/Vp)}*{1-(Vgs/Vp)}
2mA/V={(2*Idss)/-1)}*{1-(-2/-1)}
No bias drain current(Idss) = 1mA
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14. What is the drain current of an n-channel JFET (Junction Field effect transistor) if its gate to source voltage is -2Volts, pinch-off voltage is -1 volts and no bias drain current is 1miliampere?
a) -15mA
b) 6mA
c) 2mA
d) -8mA
View Answer

Answer: a
Explanation: Given:
Gate to source voltage(Vgs) = -4Volts
Pinch-off voltage(Vp) = -1volts
No bias drain current(Idss) = 1mA
From Shockleys equation we know; Drain current (Id)=(Idss)*{1-(Vgs/Vp)2}
Drain current (Id)=(1)*{1-(-4/-1)2}=>-15mA

15. What is the no bias drain to source current of an n-channel JFET (Junction Field effect transistor) if its gate to source voltage is -3Volts, pinch-off voltage is -1 volts and drain current is -24 miliampere?
a) 5mA
b) 16mA
c) 3mA
d) 8mA
View Answer

Answer: c
Explanation: Given:
Gate to source voltage(Vgs) = -3Volts
Pinch-off voltage(Vp) = -1volts
Drain current = -24 miliampere
From Shockleys equation we know; Drain current (Id)=(Idss)*{1-(Vgs/Vp)2}
-24 = ( Idss)*{1-(-3/-1)2}
Idss = 3 milliampere

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn