Semiconductor Electronics Practice Questions - DPP for JEE

 Page 1


PART-I (Single Correct MCQs)
1. A pure semiconductor has equal electron and hole concentration of 10
16
m
–3
. Doping by indium increases number of hole concentration n
h
 to 5 ×
10
22
 m
–3
. Then, the value of number of electron concentration n
e
 in the
doped semiconductor is
(a) 10
6
/m
3
(b) 10
22
/m
3
(c) 2 × 10
6
/m
3
(d) 2 × 10
9
/m
3
2. A change of 8.0 mA in the emitter current bring a change of 7.9 mA in
the collector current. The values of parameters a and ß are respectively
(a) 0.99, 90
(b) 0.96,79
(c) 0.97,99
(d) 0.99,79
Page 2


PART-I (Single Correct MCQs)
1. A pure semiconductor has equal electron and hole concentration of 10
16
m
–3
. Doping by indium increases number of hole concentration n
h
 to 5 ×
10
22
 m
–3
. Then, the value of number of electron concentration n
e
 in the
doped semiconductor is
(a) 10
6
/m
3
(b) 10
22
/m
3
(c) 2 × 10
6
/m
3
(d) 2 × 10
9
/m
3
2. A change of 8.0 mA in the emitter current bring a change of 7.9 mA in
the collector current. The values of parameters a and ß are respectively
(a) 0.99, 90
(b) 0.96,79
(c) 0.97,99
(d) 0.99,79
3. The following circut diagram represents
(a) OR gate
(b) XOR gate
(c) AND gate
(d) NAND gate
4. The correct truth table for system of four NAND gates as shown in
figure is :
(a)
(b)
Page 3


PART-I (Single Correct MCQs)
1. A pure semiconductor has equal electron and hole concentration of 10
16
m
–3
. Doping by indium increases number of hole concentration n
h
 to 5 ×
10
22
 m
–3
. Then, the value of number of electron concentration n
e
 in the
doped semiconductor is
(a) 10
6
/m
3
(b) 10
22
/m
3
(c) 2 × 10
6
/m
3
(d) 2 × 10
9
/m
3
2. A change of 8.0 mA in the emitter current bring a change of 7.9 mA in
the collector current. The values of parameters a and ß are respectively
(a) 0.99, 90
(b) 0.96,79
(c) 0.97,99
(d) 0.99,79
3. The following circut diagram represents
(a) OR gate
(b) XOR gate
(c) AND gate
(d) NAND gate
4. The correct truth table for system of four NAND gates as shown in
figure is :
(a)
(b)
(c)
(d)
5. A Zener diode is connected to a battery and a load as show below:
The currents, I, I
Z
 and I
L
 are respectively.
(a) 15 mA, 5 mA, 10 mA
(b) 15 mA, 7.5 mA, 7.5 mA
(c) 12.5 mA, 5 mA, 7.5 mA
(d) 12.5 mA, 7.5 mA, 5 mA
6. The circuit diagram shows a logic combination with the states of
outputs X, Y and Z given for inputs P, Q, R and S all at state 1. When
inputs P and R change to state 0 with inputs Q and S still at 1, the states
of outputs X, Y and Z change to
Page 4


PART-I (Single Correct MCQs)
1. A pure semiconductor has equal electron and hole concentration of 10
16
m
–3
. Doping by indium increases number of hole concentration n
h
 to 5 ×
10
22
 m
–3
. Then, the value of number of electron concentration n
e
 in the
doped semiconductor is
(a) 10
6
/m
3
(b) 10
22
/m
3
(c) 2 × 10
6
/m
3
(d) 2 × 10
9
/m
3
2. A change of 8.0 mA in the emitter current bring a change of 7.9 mA in
the collector current. The values of parameters a and ß are respectively
(a) 0.99, 90
(b) 0.96,79
(c) 0.97,99
(d) 0.99,79
3. The following circut diagram represents
(a) OR gate
(b) XOR gate
(c) AND gate
(d) NAND gate
4. The correct truth table for system of four NAND gates as shown in
figure is :
(a)
(b)
(c)
(d)
5. A Zener diode is connected to a battery and a load as show below:
The currents, I, I
Z
 and I
L
 are respectively.
(a) 15 mA, 5 mA, 10 mA
(b) 15 mA, 7.5 mA, 7.5 mA
(c) 12.5 mA, 5 mA, 7.5 mA
(d) 12.5 mA, 7.5 mA, 5 mA
6. The circuit diagram shows a logic combination with the states of
outputs X, Y and Z given for inputs P, Q, R and S all at state 1. When
inputs P and R change to state 0 with inputs Q and S still at 1, the states
of outputs X, Y and Z change to
(a) 1, 0, 0
(b) 1, 1, 1
(c) 0, 1, 0
(d) 0, 0, 1
7. A sinusoidal voltage of amplitude 25 volt and frequency 50Hz is
applied to a half wave rectifier using P-n junction diode. No filter is
used and the load resistance is 1000?. The forward resistance R
f
 of
ideal diode is 10?. The percentage efficiency of rectifier is
(a) 40%
(b) 20%
(c) 30%
(d) 15%
8. The circuit has two oppositively connected ideal diodes in parallel. The
current flowing in the circuit is
(a) 1.71 A   
(b) 2.00 A
(c) 2.31 A
(d) 1.33 A
9. A working transistor with its three legs marked P, Q and R is tested
using a multimeter. No conduction is found between P and Q. By
connecting the common (negative) terminal of the multimeter to R and
the other (positive) terminal to P or Q, some resistance is seen on the
multimeter. Which of the following is true for the transistor?
(a) It is an npn transistor with R as base
(b) It is a pnp transistor with R as base
(c) It is a pnp transistor with R as emitter
(d) It is an npn transistor with R as collector
10. The diagram of a logic circuit is given below. The output F of the
Page 5


PART-I (Single Correct MCQs)
1. A pure semiconductor has equal electron and hole concentration of 10
16
m
–3
. Doping by indium increases number of hole concentration n
h
 to 5 ×
10
22
 m
–3
. Then, the value of number of electron concentration n
e
 in the
doped semiconductor is
(a) 10
6
/m
3
(b) 10
22
/m
3
(c) 2 × 10
6
/m
3
(d) 2 × 10
9
/m
3
2. A change of 8.0 mA in the emitter current bring a change of 7.9 mA in
the collector current. The values of parameters a and ß are respectively
(a) 0.99, 90
(b) 0.96,79
(c) 0.97,99
(d) 0.99,79
3. The following circut diagram represents
(a) OR gate
(b) XOR gate
(c) AND gate
(d) NAND gate
4. The correct truth table for system of four NAND gates as shown in
figure is :
(a)
(b)
(c)
(d)
5. A Zener diode is connected to a battery and a load as show below:
The currents, I, I
Z
 and I
L
 are respectively.
(a) 15 mA, 5 mA, 10 mA
(b) 15 mA, 7.5 mA, 7.5 mA
(c) 12.5 mA, 5 mA, 7.5 mA
(d) 12.5 mA, 7.5 mA, 5 mA
6. The circuit diagram shows a logic combination with the states of
outputs X, Y and Z given for inputs P, Q, R and S all at state 1. When
inputs P and R change to state 0 with inputs Q and S still at 1, the states
of outputs X, Y and Z change to
(a) 1, 0, 0
(b) 1, 1, 1
(c) 0, 1, 0
(d) 0, 0, 1
7. A sinusoidal voltage of amplitude 25 volt and frequency 50Hz is
applied to a half wave rectifier using P-n junction diode. No filter is
used and the load resistance is 1000?. The forward resistance R
f
 of
ideal diode is 10?. The percentage efficiency of rectifier is
(a) 40%
(b) 20%
(c) 30%
(d) 15%
8. The circuit has two oppositively connected ideal diodes in parallel. The
current flowing in the circuit is
(a) 1.71 A   
(b) 2.00 A
(c) 2.31 A
(d) 1.33 A
9. A working transistor with its three legs marked P, Q and R is tested
using a multimeter. No conduction is found between P and Q. By
connecting the common (negative) terminal of the multimeter to R and
the other (positive) terminal to P or Q, some resistance is seen on the
multimeter. Which of the following is true for the transistor?
(a) It is an npn transistor with R as base
(b) It is a pnp transistor with R as base
(c) It is a pnp transistor with R as emitter
(d) It is an npn transistor with R as collector
10. The diagram of a logic circuit is given below. The output F of the
circuit is represented by
(a) W . (X + Y)
(b) W . (X . Y)
(c) W + (X . Y)
(d) W + (X + Y)
11. The concentration of hole-electron pairs in pure silicon at  T = 300 K is
7 × 10
15
 per cubic meter. Antimony is doped into silicon in a proportion
of 1 atom in 10
7
 Si atoms. Assuming half of the impurity atoms
contribute electron in the conduction band, calculate the factor by
which the number of charge carriers increases due to doping. The
number of silicon atoms per cubic meter is 5 × 10
28
(a) 2.8 × 10
5
(b) 3.1 × 10
2
(c) 4.2 × 10
5
(d) 1.8 × 10
5
12. In a common emitter (CE) amplifier having a voltage gain G, the
transistor used has transconductance 0.03 mho and current gain 25. If
the above transistor is replaced with another one with transconductance
0.02 mho and current gain 20, the voltage gain will be
(a) 1.5 G
(b) G
(c) G
(d) G
13. Which of the junction diodes shown below are forward biased?