50 Most FET Questions and Answers

1. A JFET has three terminals, namely …………
1. cathode, anode, grid
2. emitter, base, collector
3. source, gate, drain
4. none of the above
Ans : 3
2. A JFET is similar in operation to …………. valve
1. diode
2. pentode
3. triode
4. tetrode
Ans : 2

3. A JFET is also called …………… transistor
1. unipolar
2. bipolar
3. unijunction
4. none of the above
Ans : 1
4. A JFET is a ………… driven device
1. current
2. voltage
3. both current and voltage
4. none of the above
Ans : 2
5. The gate of a JFET is ………… biased
1. reverse
2. forward
3. reverse as well as forward
4. none of the above
Ans : 1
6. The input impedance of a JFET is …………. that of an ordinary
transistor
1. equal to
2. less than
3. more than
4. none of the above
Ans : 3
7. In a p-channel JFET, the charge carriers are …………..
1. electrons
2. holes
3. both electrons and holes
4. none of the above
Ans : 2
8. When drain voltage equals the pinch-off-voltage, then drain
current …………. with the increase in drain voltage
1. decreases
2. increases
3. remains constant
4. none of the above
Ans : 3
9. If the reverse bias on the gate of a JFET is increased, then width of
the conducting channel …………..
1. is decreased
2. is increased
3. remains the same
4. none of the above
Ans : 1
10. A MOSFET has …………… terminals
1. two
2. five
3. four
4. three
Ans : 4
11. A MOSFET can be operated with ……………..
negative gate voltage only
positive gate voltage only
positive as well as negative gate voltage
none of the above
Ans : 3
12. A JFET has ……….. power gain
small
very high
very small
none of the above
Ans : 2
13. The input control parameter of a JFET is ……………
gate voltage
source voltage
drain voltage
gate current
Ans : 1
14. A common base configuration of a pnp transistor is analogous to ………… of a
JFET
common source configuration
common drain configuration
common gate configuration
none of the above
Ans : 3
15. A JFET has high input impedance because …………
it is made of semiconductor material
input is reverse biased
of impurity atoms
none of the above
Ans : 2
16. In a JFET, when drain voltage is equal to pinch-off voltage, the depletion
layers ………
almost touch each other
have large gap
have moderate gap
none of the above
Ans : 1
17. In a JFET, IDSS is known as …………..
drain to source current
drain to source current with gate shorted
drain to source current with gate open
none of the above
Ans : 2
18. The two important advantages of a JFET are …………..
high input impedance and square-law property
inexpensive and high output impedance
low input impedance and high output impedance
none of the above
Ans : 1
19. …………. has the lowest noise-level
triode
ordinary trnsistor
tetrode
JFET
Ans : 4

20. A MOSFET is sometimes called ………. JFET
many gate
open gate
insulated gate
shorted gate
Ans : 3
21. Which of the following devices has the highest input impedance?
JFET
MOSFET
Crystal diode
ordinary transistor
Ans : 2
22. A MOSFET uses the electric field of a ………. to control the channel current
capacitor
battery
generator
none of the above
Ans : 1
23. The pinch-off voltage in a JFET is analogous to ………. voltage in a vacuum
tube
anode
cathode
grid cut off
none of the above
Ans : 3
25. In class A operation, the input circuit of a JFET is ………. biased
forward
reverse
not
none of the above
Ans : 2
26. If the gate of a JFET is made less negative, the width of the conducting
channel……….
remains the same
is decreased
is increased
none of the above
Ans : 3
27. The pinch-off voltage of a JFET is about ……….
5 V
0.6 V
15 V
25 V
Ans : 1
28. The input impedance of a MOSFET is of the order of ………..
Oa
few hundred O
kO
several MO
Ans : 4
29. The gate voltage in a JFET at which drain current becomes zero is
called ……….. voltage
saturation
pinch-off
active
cut-off
Ans : 2
31. In a FET, there are ……….. pn junctions at the sides
three
four
five
two
Ans : 4
32. The transconductance of a JFET ranges from ……………..
100 to 500 mA/V
500 to 1000 mA/V
0.5 to 30 mA/V
above 1000 mA/V
Ans : 3
33. The source terminal of a JEFT corresponds to ………….. of a vacuum tube
plate
cathode
grid
none of the above
Ans : 2
34. The output characteristics of a JFET closely resemble the output
characteristics of a ………. valve
pentode
tetrode
triode
diode
Ans : 1

35. If the cross-sectional area of the channel in n-channel JEFT increases, the
drain current ……….
is increased
is decreased
remains the same
none of the above
Ans : 1
36. The channel of a JFET is between the …………….
gate and drain
drain and source
gate and source
input and output
Ans : 2
37. For VGS = 0 V, the drain current becomes constant when VDS exceeds ………
cut off
VDD
VP
o V
Ans : 3
38. A certain JFET data sheet gives VGS(off) = -4 V. The pinch-off voltage Vp
is ……..
+4 V
-4 V
dependent on VGS
data insufficient
Ans : 1
39. The constant-current region of a JFET lies between
cut off and saturation
cut off and pinch-off
o and IDSS
pinch-off and breakdown
Ans : 4
40. At cut-off, the JFET channel is ……….
at its widest point
completely closed by the depletion region
extremely narrow
reverse baised
Ans : 2
41. A MOSFET differs from a JFET mainly because ………………
of power rating
the MOSFET has two gates
the JFET has a pn junction
none of the above
Ans : 3

42. A certain D-MOSFET is biased at VGS = 0 V. Its data sheet specifies IDSS =
20mA and VGS(off) = -5 V. The value of the drain current is …………
20 mA
0 mA
40 mA
10 mA
Ans : 1
43. A n-channel D-MOSFET with a positive VGS is operating in …………
the depletion-mode
the enhancement-mode
cut off
saturation
Ans : 2
44. A certain p-channel E-MOSFET has VGS(th) = -2V. If VGS= 0V, the drain
current is ……….
0 mA
ID(on)
maximum
IDSS
Ans : 1
45. In a common-source JFET amplifier, the output voltage is …………………
180o out of phase with the input
in phase with the input
90o out of phase with the input
taken at the source
Ans : 1
46. In a certain common-source D-MOSFET amplifier, Vds =3.2 V r.m. and Vgs =
280 mV r.m.s. The voltage gain is …………
11
1.4
8.75
3.2
Ans : 2
47. In a certain CS JFET amplifier, RD= 1kO , RS= 560 O , VDD=10V and gm=
4500 μS. If the source resistor is completely bypassed, the voltage gain is …………
450
45
2.52
4.5
Ans : 4

48. A certain common-source JFET has a voltage gain of 10. If the source bypass
capacitor is removed, ……………….
the voltage gain will increase
the transconductance will increase
the voltage gain will decrease
the Q-point will shift
Ans : 3
49. A CS JFET amplifier has a load resistance of 10 kO , RD= 820O . If gm= 5mS
and Vin= 500 mV, the output signal voltage is ………..
2.05 V
25 V
0.5 V
1.89 V
Ans : 4
50. If load resistance in the above question (Q.49) is removed, the output voltage
will …………
increase
decrease
stay the same
be zero
Ans : 1