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Objective Questions

Short notes

Objective questions (Answers are given below)

A FET consists of a
(a) source (b) drain
(c) gate (d) all of the above.
FETs have similar properties to
(a) PNP transistors
(b) NPN transistors
(c) thermonic valves
(d) unijunction transistors.
For small values of drain-to-source voltage,
JFET behaves like a
(a) resistor
(b) constant-current source
(c) constant-voltage source
(d) negative resistance
In a JFET, the primary control on drain current
is exerted by
(a) channel resistance
(b) size of depletion regions
(c) voltage drop across channel
(d) gate reverse bias.
After VDS reaches pinch-off value VP in a JFET,
drain current ID becomes
(a) zero (b) low
(c) saturated (d) reversed.
In a JFET, as external bias applied to the gate
is increased
(a) channel resistance is decreased
(b) drain current is increased
(c) pinch-off voltage is reached at lower val
ues of ID.
(d) size of depletion regions is reduced.
In a JFET, drain current is maximum when VGS is
(a) zero (b) negative
(c) positive (d) equal to Vp
The voltage gain of a given common- source
JFET amplifier depends on its
(a) input impedance
(b) amplification factor
(c) dynamic drain resistance
(d) drain load resistance.
A JFET has the disadvantage of
(a) being noisy
(b) having small gain-bandwidth product
(c) possessing positive temperature coe- fficient
(d) having low input impedance.
A JFET can be cut-off with the help of
(a) VGS (b) VDS
(c) VDG (d) VDD .

The drain source voltage at which drain
current becomes nearly constant is called
(a) barrier voltage
(b) breakdown voltage
(c) pick-off voltage
(d) pinch-off voltage
An FET source follower circuit has of 2
millimho and of 50 k Ω. If the source resistance
RS is 1k Ω, the output resistance of the
amplifier will be
(a) 330 Ω (b) 450 Ω
(c) 500 Ω (d) 1 k Ω
A DE MOSFET differs from a JFET in the
sense that it has no
(a) channel (b) gate
(c) P-N junctions (d) substrate.
For the operation of enhancement only N-channel
MOSFET, value of gate voltage has to be
(a) high positive (b) high negative
(c) low positive (d) zero.
The extremely high input impedance of a
MOSFET is primarily due to the
(a) absence of its channel
(b) negative gate-source voltage
(c) depletion of current carriers
(d) extremely small leakage current of its gate
capacitor
The main factor which makes a MOSFET likely
to break down during normal hand- ling is its
(a) very low gate capacitance
(b) high leakage current
(c) high input resistance
(d) both (a) and (c)
The main factor which differentiates a DE
MOSFET from an E-only MOSFET is the absence
of
(a) insulated gate (b) electrons
(c) channel (d) P-N junctions.
The polarity of VGS for E-only MOSFET is
(a) positive
(b) negative
(c) zero
(d) depends on P-or N-channel.
A transconductance amplifier has
(a) high input impedance and low output
impedance
(b) low input impedance and high output
impedance
(c) high input and output impedances
(d) low input and output impedances
The threshold voltage of an n-channel
enhancement mode MOSFET is 0.5 V, when
the device is biased at a gate voltage of 3V,
pinch-off would occur at a drain voltage of
(a) 1.5 V (b) 2.5 V
(c) 3.5 V (d) 4.5 V
The zero gate bias channel resistance of a
junction field-effect transistor is 750 and the
pinch-off voltage is 3V. For a gate bias of 1.5
V and very low drain voltage, the device
would behave as a resistance of
(a) 320 Ω (b) 816 Ω
(c) 1000 Ω (d) 1270 Ω

(d) 2. (b) 3. (a) 4. (d) 5. (c) 6. (c) 7. (a) 8. (d) 9. (b) 10. (a) 11. (d) 12. c 13. (c) 14. (a) 15. (d). 16. (d) 17. (c) 18. (d) 19. (a) 20. (c) 21. (b)

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