1987
1.
The diffusion capacitance of a PN
junction
a.
Decreases with increasing current
and increasing temperature
b.
Decreases with decreasing current
and increasing temperature
c.
Increases with increasing current
and increasing temperature
d.
Does not depend on current and
temperature
Answer: B
Solution : https://www.youtube.com/watch?v=YgQjfNh4JiU
1988
1.
For a PN junction, Match the type of
breakdown with phenomenon
i.
Avalanche breakdown
ii.
Zener breakdown
iii.
Punch through
a.
Collision of carriers with crystal
ions
b.
Early effect
c.
Rupture of covalent bond due to
strong electric field
Answer: i-a, ii-c, iii-b
2.
In the circuit shown below, the
current voltage relationship when D1 and D2 are identical
is given by (assume Germanium diodes)
Answer: B
Solution : https://www.youtube.com/watch?v=TKrqrKu90i8
1989
1.
The switching speed of P+N
junction depends primarily on
a.
the mobility of minority carriers in
the P+ region
b.
the lifetime of minority carriers in
the P+ region
c.
the mobility of majority carriers in
the N region
d.
the lifetime of majority carriers in
the N region
Answer: B
Solution : https://www.youtube.com/watch?v=vPptctf8wSU
1990
1. In a uniformly doped abrupt PN
junction, the doping level of the N-side is four times the doping level of the
P-side. Then the ratio of the depletion layer widths is......
Answer: Wn / Wp = 1 / 4
Solution : http://www.youtube.com/watch?v=ddZ7Kuje6E8
2. In a junction diode,
a. the depletion capacitance increases with increase in the reverse bias
b. the depletion capacitance increases with decrease in the reverse bias
c. the diffusion capacitance increases with increase in the forward bias
d. The diffusion capacitance is much higher than the depletion capacitance, when it is forward biased.
Answer: B,C,D
Solution : https://www.youtube.com/watch?v=2Vmo8zKg4vY
Answer: Wn / Wp = 1 / 4
Solution : http://www.youtube.com/watch?v=ddZ7Kuje6E8
2. In a junction diode,
a. the depletion capacitance increases with increase in the reverse bias
b. the depletion capacitance increases with decrease in the reverse bias
c. the diffusion capacitance increases with increase in the forward bias
d. The diffusion capacitance is much higher than the depletion capacitance, when it is forward biased.
Answer: B,C,D
Solution : https://www.youtube.com/watch?v=2Vmo8zKg4vY
3. (a) Two ideal and
identical junction diodes (with ideality factor Ƞ
= 1) connected in series as shown below.
Show that exp(eV1/KT)
+ exp(-eV2/KT) = 2, where V1 and V2 are the voltage drop across the diodes D1
and D2.
(b) Assuming that the
current flowing through the reverse biased diode is saturated at ICO,
calculate the voltage drop across the forward biased diode. Assume KT = 26 meV.
Answer: (b) 0.018 volts
Solution : https://www.youtube.com/watch?v=qz6ZD9Y5nUo
1991
1. The small signal
capacitance of an abrupt P+N junction is 1 nF/cm2 at zero
bias. If the built in voltage is 1 volt, the capacitance at a reverse bias
voltage of 99 volts is equal to ……….
Answer: 0.1 nF/cm2
Solution : https://www.youtube.com/watch?v=OLLdXgXytOE
2. Referring to the
circuit shown, the switch is in position 1 initially and steady state
conditions exist from time t=0 to t=t0. The switch is suddenly
thrown into position 2. The current I flowing through the 10K resistor as
function of time from t=0 is ………. (Give
the sketch showing the magnitudes of the current at t=0, t=t0 and t=∞)
Answer:
Solution : https://www.youtube.com/watch?v=DXWskHsBxT0
3. In the figure shown,
the input Vi is a 100 Hz triangular wave having a peak to peak
amplitude of 2 volts and an average value of zero volts. Given that the diode
is ideal, the average value of the output voltage Vo is ……………..
Answer: zero volts
Solution : https://www.youtube.com/watch?v=Kxx2qeYfk7E
4. The current in a
forward biased P+N junction shown in figure (a) is entirely due to
diffusion of holes from x = 0 to x = L. The injected hole concentration distribution
in the n-region is linear as shown in figure (b), with P(0) = 1022
per cm3 and L = 10-3 cm. Determine
a. The current density
in the diode, assuming that the diffusion coefficient of holes is 12 cm2/sec.
b. The velocity of holes
in the n-region at x = 0.
Answer:
Jn = 19.2 x 106 A/cm2
υn = 12 x 103 cm/sec
Solution : https://www.youtube.com/watch?v=fJJ5YtXBBnA
1992
1.
A PN junction with a 100 Ω resistor is forward biased so that a current of 100 mA
flows. If the voltage across this combination is instantaneously reversed to 10
volts at t = 0, the reverse current that flows through the diode at t = 0 is
approximately given by
a.
0 mA
b.
100 mA
c.
200 mA
d.
50 mA
1993
1.
In the figure, the ideal moving iron
voltmeter M will read
Answer: B
Solution : https://www.youtube.com/watch?v=5bK9WaHVqaM
2.
M in the figure shown is a rectifier
type 200 volts full scale voltmeter having a sensitivity of 10 KΩ/volt. What will be the reading in M if the source voltage VS
is a symmetrical square wave of 800 volts peak to peak ?
Answer:
Solution :
3.
The built in potential (Diffusion
potential) in a PN junction………
a.
Is equal to the difference in the Fermi
level of the two sides, expressed in volts
b.
Increases with the increase in the doping
levels of the two sides
c.
Increases with the increase in
temperature
d.
Is equal to the average of the Fermi
levels of the two sides
Answer: A & B
Solution : https://www.youtube.com/watch?v=h9awFNgU-o8
4.
Consider the circuit shown in figure
(a). if the diode used here has the V-I characteristics as shown in figure (b),
then the output waveform Vo is
1994
1.
The forward dynamic resistance of a
junction diode varies ……………… as the forward current.
Answer: Inversely
Solution : https://www.youtube.com/watch?v=HfjrpzG7j8s
1995
1.
The diffusion potential across a PN
junction
a.
Decreases with increasing doping
concentration
b.
Increases with decreasing band gap
c.
Does not depend on doping
concentration
d.
Increases with increase in doping
concentrations
Answer: D
Solution : https://www.youtube.com/watch?v=aoeFCtKOuq8
2.
The depletion capacitance, CJ,
of an abrupt PN junction with constant doping on either side varies with
reverse bias, VR as
Answer: C
Solution : https://www.youtube.com/watch?v=H7843qbzIOI
3. Two identical silicon junction diodes, D1 and D2 are
connected back to back as shown. The reverse saturation current IS
of each diode is 10-8 Amps and the breakdown voltage is 50 volts.
Evaluate the voltage VD1 and VD2 across the diode D1 and
D2 by assuming KT/q to be 25mV.
Answer: -4.98 volts and 0.018 volts
Solution : https://www.youtube.com/watch?v=i-pu6FQW5w0
1996
1.
The p-type substrate in a
conventional PN junction isolated integrated circuit should be connected to
a.
Nowhere, i.e. left floating
b.
A dc ground potential
c.
The most positive potential
available in the circuit
d.
The most negative potential
available in the circuit
Answer: D
Solution : https://www.youtube.com/watch?v=11c5h0T1g_Y
1997
1.
In the circuit shown, the current
flowing through the ideal diode equal to
a.
0 Amp
b.
4 Amp
c.
1 Amp
d.
None of the above
Answer: C
Solution : https://www.youtube.com/watch?v=lsgn8Hnz6HE
1998
1.
The static characteristic of an
adequately forward biased PN junction is a straight line, if the plot is of
a.
Log I vs. log V
b.
Log I vs. V
c.
I vs. log V
d.
I vs. V
Answer: B
Solution : https://www.youtube.com/watch?v=dsHsIn6LSls
1999
2000
1.
For the circuit in figure shown, the
voltage Vo is
a. 2 volts
b. 1 volts
c. -1 volts
d. None of the above
Answer: D
Solution : https://www.youtube.com/watch?v=wtNGel7O7ic
2001
1.
For the circuit shown in figure, D1
and D2 are identical diodes with ideality factor of unity. The
thermal voltage VT = 25 mV.
a. If the reverse saturation current, IS, for the
diode is 1 pA, then compute the current I through the circuit.
b. Calculate Vf and Vr.
Answer: (a) 1 pA (b) 0.018 mV and 0.032 mV
Solution
: https://www.youtube.com/watch?v=cK8_pacEAZY
2002
1.
In the figure shown, a silicon diode
is carrying a constant current of 1 mA. When the temperature of the diode is 20oC, diode voltage is found to be 700 mV. If the temperature
rises to 40oC, diode voltage becomes approximately equal to
a. 740 mV
b. 660 mV
c. 680 mV
d. 700 mV
Answer: B
Solution : https://www.youtube.com/watch?v=wqUUbrQy-CI
2003
1.
At 300oK, for a diode
current of 1 mA, a certain Germanium diode requires a forward bias of 0.1435
volts, where as a certain Silicon diode requires a forward bias of 0.718 volts.
Under the conditions stated above, the closest approximation of the ratio of
reverse saturation current in Ge to that of Si diode is
a. 1
b. 5
c. 4 x 103
d. 8 x 103
Answer: C
Solutoin : https://www.youtube.com/watch?v=8mEekTAFoYU
2004
1.
In abrupt PN junction, the doping
concentrations on the P side and N side are NA = 9 x 1016
cm-3 and ND = 1 x 1016 cm-3
respectively. The PN junction is reverse biased and the total depletion width
is 3 µm.
The depletion width on the P side is
a. 2.7 µm
b. 0.3 µm
c. 2.25 µm
d. 0.75 µm
Answer: B
Solution : https://www.youtube.com/watch?v=XyzrofQ1DsI
2.
Consider an abrupt PN junction. Let
Vbi be the built in potential of this junction and VR be
the applied reverse bias. If the junction capacitance (CJ) is 1 pF
for Vbi + VR = 1 volt, then for Vbi + VR
= 4 volts, the value of CJ will be
a. 4 pF
b. 2 pF
c. 0.25 pF
d. 0.75 pF
Answer: C
Solution : https://www.youtube.com/watch?v=3jTOs2F7oHA
2005
1.
A silicon PN junction at a
temperature of 20oC has a reverse saturation current of 10 pA. The
reverse saturation current at 40oC for the same bias is
approximately
a. 30 pA
b. 40 pA
c. 50 pA
d. 60 pA
Answer: B
Solution : https://www.youtube.com/watch?v=is4Hb5QGpHg
2.
A silicon PN junction diode under
reverse bias has depletion region of width of 10 µm. The relative permittivity of silicon (Ԑr) is 11.7
and the permittivity of free space (Ԑo) is 8.85
x 10-12 F/m. The depletion capacitance of the diode per square meter
is
a. 100 µF
b. 10 µF
c. 1 µF
d. 20 µF
Answer: B
Solution : https://www.youtube.com/watch?v=rxp_jLO9dz0
2006
1.
In the circuit shown below, the
switch was connected to position 1 at t < 0, and at t = 0, it is changed to
position 2. Assume that the diode has zero voltage drop and a storage time tS.
For 0<t<tS, the voltage across the 1 KΩ resistor (VR) in volts is
Answer: A
Solution : https://www.youtube.com/watch?v=-CmgL0d-ztU
2. For the circuit shown below, assume the zener diode is ideal
with a breakdown voltage of 6 volts. The waveform observed across R is
Answer: B
Solution : https://www.youtube.com/watch?v=wjeTnzvlyrw
2007
1.
In a P+N junction diode
under reverse bias, the magnitude of electric field is maximum at
a. The edge of the depletion region on P side
b. The edge of the depletion region on N side
c. The P+N junction
d. The centre of the depletion region on the N side
Answer: C
Solution : https://www.youtube.com/watch?v=986MG7ote5w
2.
The correct full wave rectifier
circuit is :
Answer: C
Solution : https://www.youtube.com/watch?v=qzbqzCNqYSA
3.
A P+N junction has a
built in potential of 0.8 volts. The depletion layer width at a reverse bias of
1.2 volts is 2 µm.
For a reverse bias of 7.2 volts, the depletion layer width will be
a. 4 µm
b. 4.9µm
c. 8
µm
d. 12
µm
Answer: A
Solution : https://www.youtube.com/watch?v=YhbWy1waleM
2008
1.
Which of the following is NOT
associated with a PN junction?
a. Junction capacitance
b. Charge storage capacitance
c. Depletion capacitance
d. Channel length modulation
Answer: D
Solution : https://www.youtube.com/watch?v=7kYKPLc5ujM
2.
In the following limiter circuit, an
input voltage Vi = 10sin100πt applied. Assume that the diode drop is 0.7 volts when it
is forward biased. The zener breakdown voltage is 6.8 volts.
The maximum and minimum values of
the output voltage respectively are
a. 6.1 volts, -0.7 volts
b. 0.7 volts, -7.5 volts
c. 7.5 volts, -0.7 volts
d. 7.5 volts, -7.5 volts
Answer: C
Solution : https://www.youtube.com/watch?v=2LAYX1bdh5o
2009
1.
In the circuit below, the diode is
ideal. The voltage V is given by
a. Min(Vi,1)
b. Max(Vi,1)
c. Min(-Vi,1)
d. Max(-Vi,1)
Answer: D
Solution : https://www.youtube.com/watch?v=yMHePwsPly0
2.
Common Data Question:
Consider a silicon PN junction at
room temperature having the following parameters:
Doping on the N side = 1x1017
cm-3
Depletion width on N side = 0.1 µm
Depletion width on the P side = 1 µm
Intrinsic carrier concentration =
1.4x1010 cm-3
Thermal voltage = 26 mV
Permittivity of free space = 8.85x10-14
F/cm
Dielectric constant of silicon = 12
i.
The built in potential of the
junction is
a.
0.70 volts
b. 0.76 volts
c.
0.82 volts
d. Cannot be estimated from given data
Answer: B
ii. The peak electric field in the device is
a.
0.15 Mvolts/cm, directed from P
region to N region
b. 0.15 Mvolts/cm, directed from N region to P region
c.
1.80 Mvolts/cm, directed from P
region to N region
d. 1.80 Mvolts/cm, directed from N region to P region
Answer: B
Solution : https://www.youtube.com/watch?v=ZbOv57yZfQg
2010
1.
Compared to a PN junction with ND=NA=1014
per cm3, which one of the following statements is TRUE for a PN
junction with NA=ND=1020 per cm3?
a. Reverse breakdown voltage is lower and depletion capacitance
is lower
b. Reverse breakdown voltage is higher and depletion
capacitance is lower
c. Reverse breakdown voltage is lower and depletion capacitance
is higher
d. Reverse breakdown voltage is higher and depletion
capacitance is higher
Answer: C
Solution : https://www.youtube.com/watch?v=wEzN6onF2AA
2011
1.
A silicon PN junction is forward
biased with a constant current at room temperature. When the temperature is
increased by 10oC, the forward bias voltage across the PN junction
a. Increases by 60 mV
b. Decreases by 60 mV
c. Increases by 25 mV
d. Decreases by 25 mV
Answer: D
Solution : https://www.youtube.com/watch?v=tOiFRbBhJfY
2012
1.
The I – V characteristics of the
diode in the circuit is given below, then the current in the circuit is
a. 10 mA
b. 9.3 mA
c. 6.67 mA
d. 6.2 mA
Answer: D
Solution : https://www.youtube.com/watch?v=I43NtISx1gc
2.
The diodes and capacitors shown in
the circuit are ideal. The voltage V(t) across the diode D1 is
2013
1.
For a forward biased PN junction
diode, the sequence of events that best describes the mechanism of current flow
is
a. Injection and subsequent diffusion and recombination of
minority carriers
b. Injection and subsequent drift and generation of minority
carriers
c. Extraction and subsequent diffusion and generation of
minority carriers
d. Extraction and subsequent drift and recombination of
minority carriers
Answer: A
Solution : https://www.youtube.com/watch?v=uADJe1kw8ag
2014
Set – 1 (15th February 2014 (Forenoon))
1.
In the figure, assume that the
forward voltage drops to the PN diode D1 and Schottky diode D2
are 0.7 volts and 0.3 volts respectively. If ON denotes conducting state of the
diode and OFF denotes the non conducting state of the diode, then in the
circuit,
a. Both are ON
b. D1 is ON and D2 is OFF
c. Both are OFF
d. D1 is OFF and D2 is ON
Answer: D
Solution : https://www.youtube.com/watch?v=qteoesfhVco
2.
The doping concentration on the P
side and N side of a silicon diode are 1x1016 cm-3 and
1x1017 cm-3 respectively. A forward bias of 0.3 volts is
applied to the diode. At T = 300oK, the intrinsic carrier
concentration of silicon, ni = 1.5 x 1010 cm-3
and KT/q = 26 mV. The electron concentration at the edge of the depletion
region on the P side is
a. 2.3 x 109 cm-3
b. 1 x 1016 cm-3
c. 1 x 1017 cm-3
d. 2.25 x 106 cm-3
Answer: A
Solution : https://www.youtube.com/watch?v=KJ1NDAVBw0U
SET – 2 (15th February 2014
(Afternoon))
1.
Consider an abrupt PN junction (at T
= 300oK) shown in the figure. The depletion region width Xn
on the N side of the junction is 0.2 µm and the permittivity of silicon (Ԑsi) is 1.044
x 10-12 F/cm. At the junction, the approximate value of the peak
electric field (in kV/cm) is………..
Answer: 30.6
Solution : https://www.youtube.com/watch?v=6SGWS0QE-dQ
2.
When a silicon diode having a doping
concentration of NA = 9 x 1016 cm-3 on P side
and ND = 1 x 1016 cm-3 on N side is reversed
biased, the total depletion width is found to be 3 µm. Given that the permittivity of silicon is 1.04 x 10-12
F/cm, the depletion width on the P side and the maximum electric field in the
depletion region, respectively, are
a. 2.7 µm
and 2.3 x 105 V/cm
b. 0.3 µm
and 4.15 x 105 V/cm
c. 0.3 µm
and 0.42 x 105 V/cm
d. 2.1 µm
and 0.42 x 105 V/cm
Answer: B
Solution : https://www.youtube.com/watch?v=PRyI9roqNbA
3.
The diode in the circuit shown, if Von
= 0.7 volts but is ideal otherwise. If Vi = 5 sin(ωt) volts, the minimum and maximum values of Vo
(in volts) are, respectively,
a. -5 and 2.7
b. 2.7 and 5
c. -5 and 3.85
d. 1.3 and 5
Answer: C
Solution : https://www.youtube.com/watch?v=VNI1bsbW2i8
SET – 3 (16th February 2014
(Forenoon))
1.
The donor and acceptor impurities in
an abrupt junction silicon diode are 1 x 1016 cm-3 and 5
x 1018 cm-3, respectively. Assume that the intrinsic
carrier concentration in silicon ni = 1.5 x 1010 cm-3
at 300oK, KT/q = 26 mV and the permittivity of silicon Ԑsi = 1.04 x
10-12 F/cm. The built in potential and the depletion width of the
diode under thermal equilibrium conditions, respectively are
a. 0.7 volts and 1 x 10-4 cm
b. 0.86 volts and 1 x 10-4 cm
c. 0.7 volts and 3.3 x 10-5 cm
d. 0.86 volts and 3.3 x 10-5 cm
Answer: D
Solution : https://www.youtube.com/watch?v=W1tmcbDY0-4
SET - 4 (16th February 2014 (Afternoon))
2015
1.
In
the circuit shown, assume that the diodes D1 and D2 are
ideal. The average value of voltage Vab (in volts), across terminals
a and b is ________________
2.
The
electric field profile in the depletion region of a PN junction in equilibrium
is shown in the figure. Which one of the following is NOT TRUE?
a.
The
left side of the junction is N-type and the right side is P-type
b.
Both
the N-type and P-type depletion regions are uniformly doped
c.
The
potential difference across the depletion region is 700 mV
d.
If
the P-type region has a doping concentration of 1015 cm-3,
then the doping concentration in the N-type region will be 1016 cm-3
Answer: C
Answer: C
Solution
:
https://www.youtube.com/watch?v=LNjwCHJv3UE
3. A region of
negative differential resistance is observed in the current voltage
characteristics of a silicon PN junction if
a.
Both
the P-region and N-region are heavily doped
b.
The
N-region is heavily doped compared to P-region
c.
The
P-region is heavily doped compared to N-region
d.
An
intrinsic silicon region is inserted between the P-region and the N-region
Answer: A
Answer: A
Solution
: https://www.youtube.com/watch?v=AfBuhR7yT50
4. For the circuit shown, assume ideal diodes. The shape of the output (Vout) for the given sine wave input (Vin) will be ________________
4. For the circuit shown, assume ideal diodes. The shape of the output (Vout) for the given sine wave input (Vin) will be ________________
5.
For a silicon diode DOPING with P and N regions, the acceptor and donor
impurity concentrations are 1x1017 cm-3 and 1x1015
cm-3 respectively. The lifetimes of electron in P-region and holes
in N-region are both 100 µs. The electron and hole diffusion coefficients are
49 cm2/sec and 36 cm2/sec respectively. Assume thermal
voltage is 26 mV, the intrinsic carrier concentration is 1x1010 cm-3
and q = 1.6x10-19 C. When a forward voltage of 208 mV is applied
across the diode, the hole current density (in nA/cm2) injected from
P-region to N-region is ___________
Answer: 28.617
Solution : https://www.youtube.com/watch?v=aR7Vz7Fm3co
Answer: 28.617
Solution : https://www.youtube.com/watch?v=aR7Vz7Fm3co
6.
The built in potential of an abrupt PN junction is 0.75 volts. If its
junction capacitance (CJ) at a reverse bias (VR) of 1.25
volts is 5 pF. The value of CJ (in pF) when VR = 7.25
volts is _____
Answer: 2.5
Solution : https://www.youtube.com/watch?v=dk28aPHYdnY
Answer: 2.5
Solution : https://www.youtube.com/watch?v=dk28aPHYdnY
7. The diode in the
circuit given below has VON = 0.7 volts but is ideal otherwise. The
current (in mA) in the 4 kΩ resistor is __________________
Can you add after 2015 gate bits to all sites of your website
ReplyDeletehere electron concentration varies linearly as shown in the above figure. concentration of electron at x=0 is N and at x=L is 0.calculate the total number of electron present in the material. given cross section area =A
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