1987
6. The pinch off voltage
for an n-channel JFET is 4 volts, then pinch off occurs for VDS when
VGS = -1 volts is
a. 3 volts
b. 5 volts
c. 4 volts
d. 1 volts
Answer: A
Solution : https://www.youtube.com/watch?v=6dIMNQ-GqKM
1988
3. In an N-channel JFET,
VGS is held constant. VDS is less than the breakdown
voltage. As VDS is increased…(Assume ‘S’ as conducting cross
sectional area of the channel and ‘J’ as channel current density)
a. ‘S’ increases and ‘J’
increases
b. ‘S’ decreases and ‘J’
decreases
c. ‘S’ decreases and ‘J’
increases
d. ‘S’ increases and ‘J’
decreases
Answer: C
Solution : https://www.youtube.com/watch?v=5wE7t_1k180
1990
6. The pinch off voltage of a JFET is 5.0 volts. Its cutoff voltage is
Answer: 5 VOLTS
Solution : https://www.youtube.com/watch?v=YZcn5Y_9p14
7. Which of the following effects can be caused by a rise in the temperature ?
a. Increase in MOSFET current
b. Increase in BJT current
c. Decrease in MOSFET current
d. Decrease in BJT current
Answer: B & C
Solution : https://www.youtube.com/watch?v=BoRoLQ2eN6o
1991
6.
The built in
potential of the gate junction of an n-channel JFET is 0.5 volts. The drain
current saturated at VDS = 5 volts when VGS = 0 volts.
The pinch off voltage is …………..
Answer: 4 VOLTS
11.
It is required to use a JFET of figure as
linear resistor. The parameters of the JFET are as follows. W = 100 µm, L = 10 µm and a = 2.5 µm. The doping in the n-layer is ND =
1016 cm-3 and the electron mobility is 1500 cm2/V-sec.
the depletion layer width of each junction due to the built in potential is
0.25 µm. The two P+ gate regions
are connected together externally. The resistances of the regions outside the
gate are negligible. Determine the minimum value of the linear resistor which
can be realized using this JFET without forward biasing the gate
junctions.
1992
5. An n-channel JFET has
a pinch off voltage VP = -5 volts, VDSmax = 20 volts, and
gm = 2 mA/V. The minimum ON resistance is achieved in the JFET for
…………
a. VGS = - 7
volts and VDS = 0 volts
b. VGS = 7 volts
and VDS = 0 volts
c. VGS = 0 volts
and VDS = 20 volts
d. VGS = - 7
volts and VDS = 20 volts
Answer: B
6. The JFET in the
circuit shown has an IDSS = 10 mA and VP = 5 volts. The
value of the resistance RS for a drain current IDS of 6.4
mA is …………….. (Select the nearest value).
1994
4. The transit time of
the current carriers through the channel of an FET decides its …………….
characteristics.
Answer: Switchimg
Solution : https://www.youtube.com/watch?v=vQJjmHNsn3I
1995
12. An n-channel JFET has IDSS =
1 mA and VP = -5 volts. Its maximum Transconductance is ……..
Answer: 0.4 mS
Solution : https://www.youtube.com/watch?v=mXxiWhP59fQ
14. In a JFET, if
Answer: a-3, b-3, c-4
Solution : https://www.youtube.com/watch?v=Ll4flWTSUbY
1996
2. A JFET with VP
= -4 volts and IDSS = 12 mA is used in the circuit shown. Assuming
the device to be operating in saturation.
a.
Determine ID,
VDS and VGS.
b.
Check to confirm that
the device is indeed operating in saturation.
Answer: 4 mA, 4 volts, -4 volts
Solution : https://www.youtube.com/watch?v=LLaKuQZnC00
1998
4. Two identical FETs,
each characterized by the parameters gm and rd are
connected in parallel. The composite FET is then characterized by the
parameters
a. gm/2 and 2rd
b. gm/2 and rd/2
c. 2gm and rd/2
d. 2gm and 2rd
Answer: C
Solution : https://www.youtube.com/watch?v=uXLjYKEeZIQ
7.. The JFET in the
circuit of figure is characterized by the parameters IDSS = 4 mA and
Vp = -4 volts.
Find (a) Vo if Vi = 0 and (b) Vi if Vo = 0
Find (a) Vo if Vi = 0 and (b) Vi if Vo = 0
Answer: (a) Vo = - VGS when Vi = 0 volts, and (b) Vi = 0.5 volts when Vo = 0 volts
Solution : https://www.youtube.com/watch?v=_5yCMN_4xO0
1999
3. An n-channel JFET has
IDSS = 2 mA and Vp = -4 volts. Its Transconductance gm
in mS for an
applied gate to source voltage of -2 volts is
a. 0.25
b. 0.50
c. 0.75
d. 1.0
Answer: B
2003
13. The action of a JFET in its equivalent
circuit can best be represented as a
a. Current controlled
current source
b. Current controlled
voltage source
c. Voltage controlled
current source
d. Voltage controlled
voltage source
Answer: C
Solutoin : https://www.youtube.com/watch?v=gF67tPBH9M8
2007
7. Group I lists four
different semiconductor devices. Match each device in Group I with its
characteristic property in Group II.
Answer: C
Solution : https://www.youtube.com/watch?v=iwERJKn2hUU
2008
10. The cross section of a JFET is shown in
the figure. Let VG be -2 volts and VP be the initial
pinch off voltage. If the width W is doubled (with other geometric parameters
and doping levels remaining the same), then the ratio between the mutual
Transconductance of the initial and the modified JFET is
Answer: B
Solution : https://www.youtube.com/watch?v=i1HcEXiUqXA
2011
7. Common Data Question:
The channel
resistance of an N channel JFET is shown below is 600 Ω, when the full channel
thickness (tOX) of 10 µm is available for conduction. The built in
voltage of the gate P+N junction is (Vbi) is -1 volts.
When the gate to source voltage (VGS) is 0 volts, the channel is
depleted by 1 µm on each side due to the built in voltage and hence the
thickness available for conduction is only 8 µm.
i.
The channel
resistance when VGS = 0 volts is
a. 480 Ω
b. 600 Ω
c. 750 Ω
d. 1000 Ω
Answer: C
ii.
The channel
resistance when VGS = -3 volt is
a. 360 Ω
b. 917 Ω
c. 1000 Ω
d. 3000 Ω
Answer: C
Solution : https://www.youtube.com/watch?v=-Nk0OFZhM-g
2015
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