# MOSFET Amplifier with CG Configuration – 2 MCQ’s

This set of Analog Electronic Circuits Multiple Choice Questions & Answers (MCQs) focuses on “MOSFET Amplifier with CG Configuration – 2″.

1. What is the input impedance of the following circuit, if channel length modulation is present?

a) g_{m} || 1/r_{o}

b) g_{m} * r_{o}

c) g_{m} || 2/r_{o}

d) g_{m}

2. The C.G. stage can be regarded as a current buffer.

a) True

b) False

3. If the inverse of transconductance is .5KS^{-1}, what should be the value of R_{c} so that the overall voltage gain is 8?

a) About 3K

b) .4K

c) About 4K

d) Such a gain is not possible

4. If M_{1} suffers from channel length modulation but M_{2} doesn’t, what is the voltage gain?

a) g_{m1} * R_{d} || 1/g_{m2} * g_{m2} * R_{d2}

b) g_{m1} * R_{d} || 1/g_{m2} * g_{m2} * 2R_{d2}

c) g_{m1} * R_{d} || 12/g_{m2} * g_{m2} * R_{d2}

d) g_{m1} * R_{d} * g_{m2} * R_{d2}

5. If channel length modulation is present, what is the total impedance at node X?

a) R_{d} || r_{o1} || 1/g_{m2}

b) R_{d} || r_{o1} || 1/g_{m2} || r_{o2}

c) R_{d} || 2r_{o1} || 1/g_{m2} || r_{o2}

d) R_{d} || r_{o1} || 2/g_{m2} || r_{o2}

6. How can we reduce the number of MOSFET’s in the following circuit?

a) Scale the aspect ratio

b) Increase the transconductance

c) Increase the Power supply

d) Not possible

7. If M_{2} suffers from channel length modulation but M_{1} doesn’t, what is the voltage gain?

a) 2g_{m1} * R_{d} || 1/g_{m2} * g_{m2} * R_{d2}

b) 2g_{m1} * R_{d} || 1/g_{m2} * g_{m2} * 2R_{d2}

c) g_{m1} * R_{d} || 12/g_{m2} * g_{m2} * R_{d2}

d) g_{m1} * R_{d} || 1/g_{m2} || r_{o2} * g_{m2} * R_{d2}

8. For an ideal current source, what is the voltage gain of the following circuit?

a) g_{m1} * r_{d1} * g_{m2} * 2R_{d2}

b) – g_{m1} * r_{d1} * g_{m2} * R_{d2}

c) 2g_{m1} * r_{d1} * g_{m2} * R_{d2}

d) – g_{m1} * r_{d1} * g_{m2} * R_{d2}

9. What is the relation between V_{b} and V_{in} in the following circuit?

a) V_{b} > V_{in} by V_{th}

b) V_{b} = V_{in}

c) V_{b} < V_{in} by V_{th}

d) No relation

10. What is the total output impedance at node x?

a) R_{1} || r_{o1} || 2 * r_{o2} || r_{o2} || 2*r_{o4} … || r_{on}

b) R_{1} || 2 * ( r_{o1} || r_{o2} … || r_{on})

c) R_{1} || r_{o1} || r_{o2 }… || r_{on}

d) R_{1} + (r_{o1} || r_{o2} … || r_{on})

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