Analog Design Interview Questions Part 2

1. In a zener diode 
(a) only the P-region is heavily doped
(b) only the N-region is heavily doped
(c) both P and N-regions are heavily doped
(d) both P and N-regions are lightly doped
2. An n-channel JEFT has IDSS= 2 mA and Vp = -4 V. Its transconductance gm (in mAV) for an applied gate to source voltage VGS of -2 V is
(a) 0.25
(b) 0.75
(c) 0.5
(d) 1.0
3. When the gate-to-source voltage (VGS) of a MOSFET with threshold voltage of 400 mV, working in saturation is 900 mV, the drain current is observed to be 1 mA. Neglecting the channel width modulation effect and assuming that the MOSFET is operating at saturation, the drain current for an applied Vas of 1400 mV Is
(a) 4 mA
(b) 2 mA
(c) 0.5 mA
(d) 3.5mA
4. Which of the following effects can be caused by a rise in the temperature?
(a) increase in MOSFET current (IDS)
(b) increase in BJT current (IC)
(c) decrease in MOSFET current (IDS)
(d) decrease in BJT current (IC)
5. In a MOSFET operating in the saturation region, the channel length modulation effect causes
(a) an increase in the gate-source capacitance
(b) a decrease in the transconductance
(c) a decrease in the unity-gain cut-off frequency
(d) a decrease in the output resistance
6. In MOSFET devices the n-channel type is better than the P-channel type in the following respects
(a) it has better noise immunity
(b) it is faster
(c) it is TTL compatible
(d) it has better drive capability
7. The drain of an n-channel MOSFET is shorted to the gate so that VGS = VDS The threshold voltage (VT) of MOSFET is 1 V. If the drain current (ID) is 1 mA for VGS = 2 V, then for VGS= 3 V. ID is
(a) 2 mA
(b) 5 mA
(c) 4 mA
(d) 9 mA
8. A diode is very useful for rectifier circuits due to its (a) ability to conduct current only in one direction
(a) ability to conduct current only in one direction
(b) ability to given current in both direction
(c) zero resistance in both direction
(d) none of these
9. A forward biased Zener diode behaves as a
(a) tunnel diode
(b) Schottky diode
(c) no diode properties
(d) ordinary diode
10. The ideal characteristics of a voltage stabilizer is
(a) constant output voltage with low Internal resistance
(b) constant output current with low Internal resistance
(c) constant output voltage with high internal resistance
(d) constant internal resistance with variable output voltage
11. A bipolar junction transistor is a 
(a) current controlled current device
(b) current controlled voltage device
(c) voltage controlled voltage device
(d) voltage controlled current device
12. One can use BJT as an amplifier in
(a) saturation region
(b) forward active region
(c) reverse active region
(d) cut-off region
13. The values of Ic and β for a transistor having IB= 100 µA and α = 98 are
(a) 49 mA, 49
(c) 4.9 mA, 49
(b) 49 mA, 50
(d) 4.9 mA, 50
14. A transistor to operate in forward active region, the required condition is
(a) emitter base junction should be forward biased and collector base junction should be reverse biased
(b) both junctions should be forward biased
(c) both junctions should be reverse biased
(d) emitter base junction should be reverse biased collector base junction should be forward biased
15. Assertion (A): The collector current in a BJT in common base mode increases slightly with increase in collector base voltage.
Reason (R): Increased collector-base bias causes avalanche breakdown to increase the
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is NOT the correct explanation of A
(c) A is true but R is false 
(d) A is false but R is true
16. An emitter in a bipolar junction transistor is doped much more heavily than the base as it reverse active increases the
(a) Emitter efficiency
(b) Base transport factor
(c) Forward current gain
(d) All the three given above
17. Early effect in BJT refers to
(a) avalanche breakdown
(b) thermal runaway
(c) base narrowing
(d) Zener breakdown
18. The maximum power dissipation capacity of a transistor is 50 mW. If the collector emitter voltage is 10 V, what is the safe collector current that can be allowed through transistor?
(a) 5 mA
(c) 10 mA
(b) 2.5 mA
(d) 25 mA
19. Consider the following statements: The bias stability of an emitter-bias amplifier circuit improves by
1. decreasing the value of RB
2. increasing the value of RE
3. decreasing the value of RE
4. increasing the value of RB
5. Increasing the value of RC
Which of the above statements are correct?
(a) 1 and 2
(c) 3 and 4
(b) 2 and 3
(d) 4 and 5
20. Thermal runaway in a transistor biased in the active region is due to
(a) heating of the transistor
(b) changes in β which increases with temperature
(c) base emitter voltage V, which decreases with rise in temperature
(d) change in reverse collector saturation current due to rise in temperature

Answer : 1. c   2. c  3. a  4. b & c  5. d  6. b  7. c  8. a  9. d  10. a  11. a  12.b  13. c 14. a  15. b  16. d  17. c  18. a  19. a


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