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Free download in PDF Op Amp Short Questions & Answers for competitive exams. These objective type questions are very important for competitive exams like IIT-JEE, GATE, CAT etc. These short solved questions or quizzes are provided by Gkseries.
41
The common-mode voltage gain of a differential amplifier is equal to RC divided by ……..
[A]
r’e
[B]
2r’e
[C]
r’e/2
[D]
2RE
42
If ground is applied to the (+) terminal of an inverting op-amp, the (–) terminal will
[A]
Not need an input resistor
[B]
Be virtual ground
[C]
Have high reverse current
[D]
Not invert the signal
Answer: Be virtual ground
43
The closed-loop voltage gain of an inverting amplifier equal to
[A]
The ratio of the input resistance to feedback resistance
[B]
The open-loop voltage gain
[C]
The feedback resistance divided by the input resistance
[D]
The input resistance
Answer: The feedback resistance divided by the input resistance
44
An amplifier using an opamp with slew rate SR=1v/sec has a gain of 40db.If this amplifier has to faithfully amplify sinusoidal signals from dc to 20KHz without introducing any slew-rate induced distortion, then the input signal level exceed
[A]
795mV
[B]
395mV
[C]
795mV
[D]
39.5mV
45
The approximate input impedance of the opamp circuit which has Ri=10k, Rf=100k, RL=10k
[A]
∞
[B]
120k
[C]
110k
[D]
10k
46
A differential amplifier has a differential gain of 20,000. CMMR=80dB. The common mode gain is given by
[A]
2
[B]
1
[C]
1/2
[D]
0
47
Which of the following amplifier is used in a digital to analog converter?
[A]
Non inverter
[B]
Voltage follower
[C]
Summer
[D]
Difference amplifier
48
When a step-input is given to an op-amp integrator, the output will be
[A]
A ramp
[B]
A sinusoidal wave
[C]
A rectangular wave
[D]
A triangular wave with dc bias
49
In the above circuit the current ix is
[A]
0.6A
[B]
0.5A
[C]
0.2A
[D]
1/12A
50
When a differential amplifier is operated single-ended, …………
[A]
the output is grounded
[B]
one input is grounded and signal is applied to the other
[C]
both inputs are connected together
[D]
the output is not inverted
Answer: one input is grounded and signal is applied to the other
51
The differential gain is ………
[A]
very high
[B]
very low
[C]
dependent on input voltage
[D]
about 100
52
With zero volts on both inputs, an OP-amp ideally should have an output ………..
[A]
equal to the positive supply voltage
[B]
equal to the negative supply voltage
[C]
equal to zero
[D]
equal to CMRR
53
Of the values listed, the most realistic value for open-loop voltage gain of an OP-amp is ……
[A]
1
[B]
2000
[C]
80 dB
[D]
100,000
54
The output of a particular Op-amp increases 8V in 12µs. The slew rate is …….
[A]
90 V/µs
[B]
0.67 V/µs
[C]
1.5 V/µs
[D]
none of these
55
Negative feedback ………..
[A]
increases the input and output impedances
[B]
increases the input impedance and bandwidth
[C]
decreases the output impedance and bandwidth
[D]
does not affect impedance or bandwidth
Answer: increases the input impedance and bandwidth
56
A voltage follower ……….
[A]
has a voltage gain of 1
[B]
is noninverting
[C]
has no feedback resistor
[D]
has all of these
57
The tail current in a differential amplifier equals …….
[A]
difference between two emitter currents
[B]
sum of two emitter currents
[C]
collector current divided by current gain
[D]
collector voltage divided by collector resistance
Answer: sum of two emitter currents
58
The input impedance of a differential amplifier equals r’e times ……
[A]
ß
[B]
RE
[C]
RC
[D]
2ß
59
The common-mode voltage gain is ………
[A]
smaller than differentail voltage gain
[B]
equal to differential voltage gain
[C]
greater than differential voltage gain
[D]
none of the above
Answer: smaller than differentail voltage gain
60
The common-mode voltage gain of a differential amplifier is equal to RC divided by ……..
[A]
r’e
[B]
2r’e
[C]
r’e/2
[D]
2RE
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