# FET – Exercise – 1

1. The JFET acts as a ……….. along vertical parts of the drain curve.

(a)  Resistor
(b)  Current source
(c)  Voltage source
(d)  Current sink

Explanation
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2. The transconductance curve of JFET which is also called as square law curve is :

(a)  Straight line
(b)  Parabolic
(c)  Circular
(d)  Wavy

Explanation
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3. Which of the following is/are valid statement(s) ?
1. The gate of a JFET is forward biased hence acts as a voltage controlled device.
2. The gate of a JFET is reversed biased, hence acts as a voltage controlled device.
3. The gate of a JFET is reverse biased, hence acts as voltage controlled device.

(a)  1
(b)  2
(c)  1 and 2
(d)  1, 2 and 3

Explanation
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4. Field effect transistor has :

(a)  large input impedance
(b)  large output impedance
(c)  large power gain
(d)  large voltage gain

Explanation
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5. In the voltage range, Vp < VDS< BVDSS of an ideal JFET or MOSFET :

(a)  the drain current varies linearly with VDS
(b)  the drain current is constant
(c)  the drain current varies non-linearly with VDS
(d)  the drain current is cut off

Explanation
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6. The transconductance, gm of a JFET is computed at constant VDS, by the following :

(a)  ∆ID/∆VGS
(b)  ∆VGS/∆ID
(c)  ∆VGSx∆ID
(d)  ∆ID/∆VGS+∆IDS

Explanation
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7. The pinch-off voltage of JFET has a same magnitude as that of :

(a)  Gate voltage
(b)  Gate source voltage
(c)  Drain–source voltage
(d)  None of these

Explanation
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8. The gate cut-off and pinch-off voltages of JFET have :

(a)  Same magnitude and sign
(b)  Different magnitudes but same sign
(c)  Same magnitude but different signs
(d)  Different magnitudes and signs

Explanation
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9. The output characteristics of a JFET is similar to :

(a)  Triode
(b)  Pentode
(c)  Thyratron
(d)  Tetrode

Explanation
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10. For small values of drain to source voltage, JFET behaves like a :

(a)  Diode
(b)  Capacitor
(c)  Inverter
(d)  Resistor

Explanation
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(a) (b) (c) (d) Answer : () [/su_spoiler]
Explanation
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12. With reference to JFET configuration, match the following
(P) Common Source Configuration         (1) No phase shift between input & output
(Q) Common Drain Configuration           (2) High input impedance & low output impedance
(R) Common Gate Configuration             (3) Source follower Configuration

(a)  P-1, Q-2, R-3
(b)  P-2, Q-3, R-1
(c)  P-2, Q-1, R-3
(d)  P-3, Q-1, R-2

Explanation
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13. Conduction modulation is exhibited by :

(a)  Transistor
(b)  Diode
(c)  JFET
(d)  Tunnel diode

Explanation
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14. Junction gate type of FET can be operated :

(a)  Only in depletion mode
(b)  Only in enhancement mode
(c)  Both depletion & enhancement modes
(d)  Either depletion or enhancement mode

Explanation
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15. The constant current area of FET lies between :

(a)  0 & IDSS
(b)  Cut off & Pinch off regions
(c)  Cut off & Saturation regions
(d)  Pinch-off & break-down regions

Explanation
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16. A BJT is …….. controlled and the FET is ………. controlled device.

(a)  Current, Current
(b)  Voltage, Voltage
(c)  Voltage, Current
(d)  Current, Voltage

Explanation
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17. The gate of FET is analogous to the …….. of BJT.

(a)  Emitter
(b)  Collector
(c)  Base
(d)  None of these

Explanation
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18. The equivalent circuit of FET contains :

(a)  A current source in series with resistance
(b)  A resistance between drain and source terminals
(c)  A current source between gate and source terminals
(d)  A current source between drain and source terminals

Explanation
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19. Which of the following statements is/are correct ?
1. The input capacitance of FET is low.
2. The transfer characteristics of FET can be represented mathematically by the Shockley equation.

(a)  Statement 1
(b)  Statement 2
(c)  Both statements 1 & 2
(d)  Either statement 1 or 2

Explanation
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20. In an ideal JFET, RGS is infinite because :

(a)  IG< 0
(b)  IG> 0
(c)  IG= 0
(d)  IG= ∞

Explanation
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21. Which is valid with respect to JFET ?

(a)  Operated in depletion and enhancement modes
(b)  Gate is not insulated from channel
(c)  Channel doesn’t permanently exist
(d)  It possesses low input impedance

Explanation
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22. An n-channel JFET having a pinch off voltage of –5 V shows a transconductance of 1 mA/V when applied gate-to-source voltage of –3 V. Then its maximum transconductance is found to be :

(a)  1.5 mA/V
(b)  2.0 mA/V
(c)  2.5 mA/V
(d)  3.0 mA/V

Explanation
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23. JFET channel is pinched-off only when :

(a)  VDD is equal to VP
(b)  VDSis greater than VP
(c)  VDSis less than VP
(d)  VDSis equal to VP

Explanation
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24. Determine the invalid statement.

(a)  For an n-channel JFET, both VGS and VP are negative
(b)  For a p-channel JFET, both VGS and VP are positive
(c)  For an n-channel JFET, IDSS is positive
(d)  For a p-channel JFET, IDSS is positive

Explanation
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25. An FET acts as :

(a)  A variable resistor
(b)  A variable capacitor
(c)  A variable voltage source
(d)  A variable current source

Explanation
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26. Consider the statements given below :
Statement I : In FET the generator current is proportional to the input voltage.
Statement II : In BJT, the generator current is proportional to the input current.
Which of the following is valid ?

(a)  Statement I
(b)  Statement II
(c)  Both statements I & II
(d)  Either statement I or II

Explanation
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27. FETs are used in an amplifier to obtain :

(a)  Low input impedance
(b)  Low output impedance
(c)  High input impedance
(d)  High output impedance

Explanation
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28. Which of the following exhibits very high input impedance ?

(a)  Diode
(b)  P-N-P
(c)  N-P-N
(d)  FET

Explanation
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29. …….. indicates how effectively the input voltage controls the output current in a JFET.

(a)  Slow rate
(b)  Transconductance
(c)  Transresistance
(d)  Intrinsic stand-off ratio

Explanation
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30. ……… is preferred form of bias for a JFET amplifier.

(a)  Self bias
(b)  Voltage divider bias
(c)  Two supply bias
(d)  Emitter feedback bias

Explanation
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31. The transconductance JFET at the Q-point is ……… the maximum transconductance which occurs when Vds = 0.

(a)  Less than
(b)  Greater than
(c)  Equal to
(d)  None of the above

Explanation
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32. A current regulator diode is basically a :

(a)  Zener diode
(b)  MOSFET
(c)  JFET whose gate and source are tied up
(d)  Transistor

Explanation
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33. A JFET has :

(a)  One built-in diode
(b)  Two built-in diodes
(c)  Three built-in diodes
(d)  Four built-in diodes

Explanation
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34. The JFET acts as a …….. along the horizontal part of the drain curve.

(a)  Resistor
(b)  Current source
(c)  Voltage source
(d)  Current sink

Explanation
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35. Which of the following is/are valid statement(s) ?
I. The gate of a JFET is forward biased hence acts as a voltage controlled device.
II. The gate of a JFET is reversed biased, hence acts as a voltage controlled device.
III. The gate of a JFET is reverse biased, hence acts as voltage controlled device.

(a)  I
(b)  II
(c)  I and II
(d)  I, II and III

Explanation
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36. FET has offset voltage of about :

(a)  0.2 volts
(b)  0.6 volts
(c)  1.0 volts
(d)  3.6 volts

Explanation
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37. The point above the drain voltage, where there is no increase in drain current in a JFET is called as :

(a)  Breakdown point
(b)  Pinch off point
(c)  Knee point
(d)  Critical point

Explanation
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38. A JFET has three terminals, namely …….

(a)  cathode, anode, grid
(b)  emitter, base, collector
(c)  source, gate, drain
(d)  none of the above

Explanation
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39. A JFET is similar in operation to ……. valve.

(a)  diode
(b)  pentode
(c)  triode
(d)  tetrode

Explanation
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40. A JFET is also called ……. transistor.

(a)  unipolar
(b)  bipolar
(c)  unijunction
(d)  none of the above

Explanation
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41. A JFET is a ……. driven device.

(a)  current
(b)  voltage
(c)  both current and voltage
(d)  none of the above

Explanation
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42. The gate of a JFET is ……. biased.

(a)  reverse
(b)  forward
(c)  reverse as well as forward
(d)  none of the above

Explanation
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43. The input impedance of a JFET is ……. that of an ordinary transistor.

(a)  equal to
(b)  less than
(c)  more than
(d)  none of the above

Explanation
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44. In a p-channel JFET, the charge carriers are …….

(a)  electrons
(b)  holes
(c)  both electrons and holes
(d)  none of the above

Explanation
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45. A JFET……… is usually the point of reference.

(a)  Gate
(b)  Drain
(c)  Source
(d)  Either b or c

Explanation
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46. The input gate current of a FET is :

(a)  A few amperes
(b)  A few milliamperes
(c)  A few micro amperes
(d)  Negligibly small

Explanation
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47. When drain voltage equals the pinch-off voltage, then drain current ……. with the increase in drain voltage.

(a)  decreases
(b)  increases
(c)  remains constant
(d)  none of the above

Explanation
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48. If the reverse bias on the gate of a JFET is increased, then width of the conducting channel …….

(a)  is decreased
(b)  is increased
(c)  remains the same
(d)  none of the above

Explanation
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49. A JFET has ……. power gain.

(a)  small
(b)  very high
(c)  very small
(d)  none of the above