This set of VLSI Multiple Choice Questions & Answers (MCQs) focuses on “Metal Oxide Semiconductor (MOS) Transistor – 2”.
1. The current through the n-MOS transistor will flow when:
a) Vgs > Vtreshold, Vds=0
b) Vgd < Vtreshold, Vds=0
c) Vgs > Vtreshold, Vds>0
d) Vgd > Vtreshold, Vds<0
View Answer
Explanation: The current flows through the n-MOS transistor when Vgs>Vtreshold, Vds>0.
2. The p-MOS Transistor is said to be in Saturation mode when:
a) Vdsp > Vgsp – Vtp
b) Vgsp < Vdsp –Vtp
c) Vgsp > Vtp
d) Vdsp < Vgsp – Vtp
View Answer
Explanation: The pMOS transistor is in Saturation mode when Vdsp < Vgsp – Vtp and Vgsp < Vtp.
3. The Fermi potential of the p-type MOSFET is :
a) φfp = (kT/q)ln(ND/NA)
b) φfp = (kT/q)ln(NA/ND)
c) φfp = (kT/q)ln(NA/ ni)
d) φfp = (kT/q)ln(ni/NA)
View Answer
Explanation: The Fermi potential of the p-type semiconductor is φfp = (kT/q)ln(ni/NA) where ni denotes the intrinsic carrier concentration of silicon, NA is acceptor concentration, ND is Donor Concentration.
4. The Fermi potential(φfp) for the n-type MOSFET is :
a) φfp = (kT/q)ln(ND/NA)
b) φfp = (kT/q)ln(NA/ND)
c) φfp = (kT/q)ln(ND/ ni)
d) φfp = (kT/q)ln(ni/ND)
View Answer
Explanation: The Fermi potential of the p-type semiconductor is φfp = (kT/q)ln(ND/ ni) where ni denotes the intrinsic carrier concentration of silicon, NA is acceptor concentration, ND is Donor Concentration.
5. The principle of the MOSFET operation is:
a) Control the conduction of current between the source and the drain, using the potential difference applied at the gate voltage as a control variable
b) Control the current conduction between the source and the gate, using the electric field applied at the drain voltage as a control variable
c) Control the current conduction between the PN junction, using the electric field generated by the bias voltage as a control variable
d) Control the current conduction between the PN junctions, using the electric potential generated by the gate voltage as a control variable
View Answer
Explanation: By varying the gate voltage the current between the source and drain are varied.
6. The conduction of current IDS depends on:
1) Gate to source voltage
2) Drain to source voltage
3) Bulk to source voltage
4) Threshold voltage
5) Dimensions of MOSFET
a) Only 1st option
b) Only 1st, 2nd and 3rd option
c) Only 5th option
d) All of the mentioned
View Answer
Explanation: The current depends on Vgs, Vds, Vbs, Vt and dimensions of MOSFET.
7. The impedance at the input of n-MOS transistor circuit is :
a) Lesser than p-MOS transistor
b) Greater than BJT transistor
c) Lesser than JFET transistor
d) Zero
View Answer
Explanation: The impedance at the input of n-MOS transistor is more than BJT transistor.
8. The depletion mode n-MOS differs from enhancement mode n-MOS in:
a) Threshold voltage
b) Channel Length
c) Switching time
d) None of the mentioned
View Answer
Explanation: If n-MOS operates with negative threshold voltage then it is in depletion mode. If n-MOS operates with positive threshold voltage then it is in enhancement mode.
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