Explore topic-wise MCQs in Electronics & Communication Engineering.

This section includes 1136 Mcqs, each offering curated multiple-choice questions to sharpen your Electronics & Communication Engineering knowledge and support exam preparation. Choose a topic below to get started.

101.

In a class C operation VCC = 40 V, RL = 50 Ω. The maximum load power can be

A. 64 W
B. 32 W
C. 16 W
D. 8 W
Answer» D. 8 W
Discussion
102.

If the output current wave shape of class C circuit has a period of 1 μs and a pulse width of 0.006 μs, the duty cycle is

A. 6%
B. 0.6%
C. 0.006%
D. 0.06%
Answer» C. 0.006%
Discussion
103.

In a class C power amplifier the input signal has a frequency of 250 kHz. If the collector current pulses are 0.1 μs wide, the duty cycle of current waveform is

A. 50%
B. 25%
C. 2.5%
D. 0.25%
Answer» D. 0.25%
Discussion
104.

In a push pull circuit the two transistors are

A. both pnp
B. both npn
C. one pnp and other npn
D. either (a) or (b)
Answer» D. either (a) or (b)
Discussion
105.

In a power amplifier the collector current flows for 270° of the input cycle. The operations is

A. class A
B. class B
C. class AB
D. class C
Answer» D. class C
Discussion
106.

In figure, IC ≈

A. I1
B. IB
C. 0.5 I1
D. 0.5 IB
Answer» B. IB
Discussion
107.

A transistor has a power rating of 8 W for a case temperature of 25°C. If derating factor is 30 mW/°C, the power rating for 55°C, case temperature is

A. 8 W
B. 7.5 W
C. 7.1 W
D. 6.8 W
Answer» D. 6.8 W
Discussion
108.

A power transistor dissipates 5 W. If ambient temperature is 30° and case to air thermal resistance is 10° C/W, the case temperature is

A. 80°C
B. 20°C
C. 32°C
D. 305°C
Answer» B. 20°C
Discussion
109.

A transistor has a maximum power dissipation of 350 mW at an ambient temperature of 25°C. If derating factor is 2 mW/°C, the maximum power dissipation for 40°C ambient temperature is

A. 300 mW
B. 330 mW
C. 350 mW
D. 380 mW
Answer» D. 380 mW
Discussion
110.

A CE amplifier has re = 6 Ω, β = 100 and a = 0.98. The input impedance is

A. 6 Ω
B. 100 Ω
C. 600 Ω
D. 98 Ω
Answer» D. 98 Ω
Discussion
111.

A CB amplifier has re = 6 Ω, RL = 600 Ω and a = 0.98. The voltage gain is

A. 100
B. 600 x 0.98
C. 98
D. 6
Answer» D. 6
Discussion
112.

In a CC circuit the current gain is

A. [A].
B. [B].
C. [C].
D. β
Answer» B. [B].
Discussion
113.

A CB amplifier has IE = 3.5 mA, a = 0.98 and RL = 600 Ω. The input impedance

A. 0.98 Ω
B. 0.025 Ω
C. [C].
D. 600 Ω
Answer» D. 600 Ω
Discussion
114.

A CB amplifier has a = 0.98 and RL = 600 Ω. If IE = 3.5 mA, the current gain is

A. 1
B. 0.98
C. 0.98 x 3.5
D. [D].
Answer» C. 0.98 x 3.5
Discussion
115.

In figure output impedance of amplifier is

A. RE
B. [B].
C. [C].
D. re + RE
Answer» D. re + RE
Discussion
116.

In figure the voltage gain is

A. [A].
B. re
C. [C].
D. [D].
Answer» D. [D].
Discussion
117.

In the equivalent circuit of figure voltage gain is

A. a
B. [B].
C. [C].
D. [D].
Answer» D. [D].
Discussion
118.

In a transistor βdc is likely to vary between 100 and 400. The proper value of βdc to be used to located Q point is

A. 100
B. 400
C. 250
D. 200
Answer» E.
Discussion
119.

In a transistor the minimum and maximum values of βdc are 100 and 121. The proper value of βdc to be used to locate Q point is

A. 100
B. 121
C. 110.5
D. 110
Answer» E.
Discussion
120.

In figure VCC = + 30 V, IC corresponding to Q point is 1 mA. If RC = 5 kΩ and RE = 5 kΩ, VCE corresponding to Q point is

A. 30 V
B. 20 V
C. 25 V
D. 5 V
Answer» C. 25 V
Discussion
121.

In figure, voltage across R2 = + 10 V. If VBE = 0.7 V and VE = 0.7 V and RE = 10 kΩ, current through RE is

A. 1 mA
B. 0.93 mA
C. 2 mA
D. 1.86 mA
Answer» C. 2 mA
Discussion
122.

In figure, VCC = + 30 V, R1 = 200 kΩ and R2 = 100 kΩ. If VBE = 0.7 V, the voltage a cross RE =

A. +20 V
B. +19.3 V
C. +10 V
D. +9.3 V
Answer» E.
Discussion
123.

In figure, transistor βdc = 100 and LED voltage when it is conducting is 2 V. Then the base current which saturates the transistor is

A. 18 mA
B. 1.8 mA
C. 0.18 mA
D. 0.018 mA
Answer» D. 0.018 mA
Discussion
124.

In figure the saturation collector current is

A. [A].
B. [B].
C. [C].
D. none of the above
Answer» D. none of the above
Discussion
125.

In figure what is value of IC if βdc = 100. Neglect VBE

A. 5 mA
B. 5 μA
C. 10 mA
D. 10 μA
Answer» D. 10 μA
Discussion
126.

In figure base current is 10 μA and βdc = 100. Then VE =

A. 5 V
B. 10 V
C. 15 V
D. 20 V
Answer» D. 20 V
Discussion
127.

For a base current of 10 μA, what is the value of collector current in common emitter if βdc = 100

A. 10 μA
B. 100 μA
C. 1 mA
D. 10 mA
Answer» D. 10 mA
Discussion
128.

In figure vi is a sinusoidal wave. Which of the following best describes the output v0?

A. [A].
B. [B].
C. [C].
D. [D].
Answer» C. [C].
Discussion
129.

A voltage doubler circuit is fed by a voltage Vm sin ωt. The output voltage will be nearly 2 Vm only if

A. load resistance is small
B. load resistance is large
C. load resistance is neither small nor large
D. either (a) or (c)
Answer» C. load resistance is neither small nor large
Discussion
130.

A half wave diode circuit using ideal diode has an input voltage 20 sin ωt volts. Then average and rms values of output voltage are

A. and 10 V
B. and 10 V
C. and 5 V
D. and 5 V
Answer» C. and 5 V
Discussion
131.

A bridge diode circuit using ideal diodes has in input voltage of 20 sin ωt volts. The average and rms values of output voltage are

A. [A].
B. [B].
C. [C].
D. [D].
Answer» B. [B].
Discussion
132.

In the diode circuit of figure the diodes are ideal. The average current through ammeter is

A. [A].
B. [B].
C. [C].
D. [D].
Answer» C. [C].
Discussion
133.

In figure, VEB = 0.6 V, β = 99. Then VC and IC are

A. 9.3 V and 1.98 mA respectively
B. 4.6 V and 1.98 mA respectively
C. 9.3 V and 0.02 mA respectively
D. 4.6 V and 0.02 mA respectively
Answer» B. 4.6 V and 1.98 mA respectively
Discussion
134.

An amplifier has input impedance of 4 kΩ and output impedance of 80 kΩ. It is used in negative feedback circuit with 10% feedback. If open loop gain is 90, the closed loop input and output impedances are

A. 40 kΩ and 8 kΩ respectively
B. 4 kΩ and 80 kΩ respectively
C. 0.4 kΩ and 800 kΩ respectively
D. 8 kΩ and 160 kΩ respectively
Answer» B. 4 kΩ and 80 kΩ respectively
Discussion
135.

In the op-amp circuit shown in figure the current through load resistance RL is

A. [A].
B. [B].
C. [C].
D. [D].
Answer» B. [B].
Discussion
136.

At the peak of negative half cycle in figure

A. diode A is forward biased and diode B is reverse biased
B. both diodes are reverse biased
C. both diodes are forward biased
D. diode A is reverse biased and diode B is forward biased
Answer» E.
Discussion
137.

In figure the cut in voltage of diode is 0.7 V and its bulk resistance is 20 Ω. The peak value of circuit current of during positive and negative half cycles are

A. 10 mA and zero
B. 9.12 mA and zero
C. 9.3 mA and zero
D. zero and 9.12 mA
Answer» C. 9.3 mA and zero
Discussion
138.

In the amplifier circuit of figure hfe = 100 and hie = 1000 Ω. The voltage gain of amplifier is about

A. 0.33
B. 0.5
C. 0.66
D. 1
Answer» E.
Discussion
139.

For the circuit in figure the output wave shape is

A. [A].
B. [B].
C. [C].
D. [D].
Answer» E.
Discussion
140.

In figure the collector to emitter breakdown voltage of the transistor (βVCEO) should be

A. more than VCC
B. more than 0.5 VCC
C. more than VCC + E
D. more than 2 VCC
Answer» C. more than VCC + E
Discussion
141.

In the re model of a BJT amplifier, the ac resistance of diode at room temperature is about (IE is quiescent emitter current)

A. [A].
B. [B].
C. [C].
D. [D].
Answer» B. [B].
Discussion
142.

In the circuit of figure β = 100 and quiescent value of base current is 20 μA. The quiescent value of collector current is

A. 0.2 μA
B. 2 μA
C. 2 mA
D. 20 mA
Answer» D. 20 mA
Discussion
143.

In the circuit of figure β = 50 and VBE = 0.5 V. The quiescent value of base current IB is

A. about 28 μA
B. about 28 mA
C. about 0.28 μA
D. about 2.8 A
Answer» B. about 28 mA
Discussion
144.

In the CE circuit shown in figure the slope of dc load line will be

A. [A].
B. [B].
C. [C].
D. [D].
Answer» B. [B].
Discussion
145.

In the CE circuit shown in figure the slope of ac load line will be

A. [A].
B. [B].
C. [C].
D. [D].
Answer» C. [C].
Discussion
146.

In an oscillator the total phase shift around the loop must be

A. 180°
B. 90°
C. 270°
D. 0°
Answer» E.
Discussion
147.

A Darlington pair has β = 300. If RE = 1 kΩ and RL = 100 Ω, the input impedance at the base is approximately

A. 300 k ohm
B. 3 k ohm
C. 100 k ohm
D. 30 k ohm
Answer» C. 100 k ohm
Discussion
148.

In a CE amplifier, the collector resistance is 6 kΩ and load resistance is 3 kΩ. The ac load resistance is

A. 9 kΩ
B. 6 kΩ
C. 3 kΩ
D. 2 kΩ
Answer» E.
Discussion
149.

A bridge rectifier circuit has a dc load current of 10 mA and a filter capacitance of 1000 μF. The peak to peak ripple voltage is

A. 0.01 V
B. 0.05 V
C. 0.1 V
D. 0.5 V
Answer» D. 0.5 V
Discussion
150.

A forward voltage of 9 V is applied to a diode in series with a 1 kΩ load resistor. The voltage across load resistor is zero. It indicates that

A. diode is short circuited
B. diode is open circuited
C. resistor is open circuited
D. diode is either short circuited or open circuited
Answer» C. resistor is open circuited
Discussion