Question 1:
The common mode gain is ___________
A.
very high
B.
very low
C.
always unity
D.
unpredictable
Answer: _________
Question 2:
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.
79.5mV
B.
395mV
C.
795mV
D.
39.5mV
Answer: _________
Question 3:
Current cannot flow to ground through .
A.
a mechanical ground
B.
an a.c. ground
C.
a virtual ground
D.
an ordinary ground
Answer: _________
Question 4:
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
Answer: _________
Question 5:
An OPAMP has a slew rate of 5 V/μS. The largest sine wave output voltage possible at a frequency of 1 MHZ is [Hint: Slew rate is defined as the max. rate of change of output voltage. Its unit is V/μS.]
A.
$$10pi { ext{V}}$$
B.
$$5{ ext{V}}$$
C.
$$frac{5}{prod }{ ext{V}}$$
D.
$$frac{5}{{2prod }}{ ext{V}}$$
Answer: _________
Question 6:
Calculate the cutoff frequency of a first-order low-pass filter for R1 = 2.5kΩ and C1 = 0.05μF
A.
1.273 kHz
B.
12.73 kHz
C.
127.3 kHz
D.
127.3 Hz
Answer: _________
Question 7:
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
Answer: _________
Question 8:
The approximate input impedance of the opamp circuit which has Ri = 10k, Rf = 100k, RL = 10k
A.
$$infty $$
B.
120k
C.
110k
D.
10k
Answer: _________
Question 9:
For an OP-amp with negative feedback, the output is .
A.
equal to the input
B.
increased
C.
fed back to the inverting input
D.
fed back to the noninverting input
Answer: _________
Question 10:
The common mode voltage gain of a differential amplifier is equal to RC divided by
A.
r e
B.
2r e
C.
$$frac{{{{ ext{r}}_{ ext{e}}}}}{2}$$
D.
2R E
Answer: _________
Question 11:
The input stage of an OP-amp is usually a ___________
A.
differential amplifier
B.
class B push-pull amplifier
C.
CE amplifier
D.
swamped amplifier
Answer: _________
Question 12:
A certain OP-amp has bias currents of 50 µA. The input offset current is
A.
700 nA
B.
99.3 µA
C.
49.7 µA
D.
none of these
Answer: _________
Question 13:
The output voltage Vo of the above circuit is
A.
-6V
B.
-5V
C.
-1.2V
D.
-0.2V
Answer: _________
Question 14:
For an OP-amp having differential gain A v and common mode gain A c the CMRR is given by
A.
$${{ ext{A}}_{ ext{V}}} + {{ ext{A}}_{ ext{C}}}$$
B.
$$frac{{{{ ext{A}}_{ ext{V}}}}}{{{{ ext{A}}_{ ext{C}}}}}$$
C.
$${{ ext{A}}_{ ext{V}}} + frac{1}{{{{ ext{A}}_{ ext{C}}}}}$$
D.
$$frac{{{{ ext{A}}_{ ext{C}}}}}{{{{ ext{A}}_{ ext{V}}}}}$$
Answer: _________
Question 15:
Which of the following amplifier is used in a digital to analog converter?
A.
Non inverter
B.
Voltage follower
C.
Summer
D.
Difference amplifier
Answer: _________
Question 16:
The input offset current equals the ___________
A.
difference between two base currents
B.
average of two base currents
C.
collector current divided by current gain
D.
none of these
Answer: _________
Question 17:
An opamp has a slew rate of 5 V/μS. The largest sine wave output voltage possible at a frequency of 1MHz is
A.
$$frac{5}{{2prod }}{ ext{V}}$$
B.
$$5{ ext{V}}$$
C.
$$frac{5}{prod }{ ext{V}}$$
D.
$$10pi { ext{V}}$$
Answer: _________
Question 18:
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: _________
Question 19:
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.
100000
Answer: _________
Question 20:
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: _________
Question 21:
A certain inverting amplifier has a closed-loop voltage gain of 25. The OP-amp has an open-loop voltage gain of 100,000. If an OP-amp with an open-loop voltage gain of 200,000 is substituted in the arrangement, the closed-loop gain
A.
doubles
B.
drops to 12.5
C.
remains at 25
D.
increases slightly
Answer: _________
Question 22:
How many OP-amps are required to implement this equation V 0 = V 1
A.
4
B.
3
C.
2
D.
1
Answer: _________
Question 23:
The input impedance of a differential amplifier equals r'e times
A.
ß
B.
RE
C.
RC
D.
2ß
Answer: _________
Question 24:
The ideal OP-AMP has the following characteristics
A.
R i = $$infty $$, A V = $$infty $$, R O = 0
B.
R i = 0, A V = $$infty $$, R O = 0
C.
R i = $$infty $$, A V = $$infty $$, R O = $$infty $$
D.
R i = 0, A V = $$infty $$, R O = $$infty $$
Answer: _________
Question 25:
A 741-Type OP-amp has a gain-bandwith product of 1MHz. A non-inverting amplifier using this opamp & having a voltage gain of 20db will exhibit -3db bandwidth of
A.
50 kHz
B.
100 kHz
C.
$$frac{{1000}}{{17}}{ ext{ kHz}}$$
D.
$$frac{{1000}}{{7.07}}{ ext{ kHz}}$$
Answer: _________
Question 26:
In the above circuit the current i x is
A.
0.6A
B.
0.5A
C.
0.2A
D.
$$frac{1}{{12}}{ ext{A}}$$
Answer: _________
Question 27:
In differential-mode, ___________
A.
opposite polarity signals are applied to the inputs
B.
the gain is one
C.
the outputs are of different amplitudes
D.
only one supply voltage is used
Answer: _________
Question 28:
Assume that the OP-amp of the fig. is ideal. If Vi is a triangular wave, then V0 will be
A.
Square wave
B.
Triangular wave
C.
Parabolic wave
D.
Sine wave
Answer: _________
Question 29:
The differential gain is
A.
very high
B.
very low
C.
dependent on input voltage
D.
about 100
Answer: _________
Question 30:
When a number of stages are connected in parallel, the overall gain is the product of the individual stage gains
A.
True
B.
False
Answer: _________
Question 31:
For an ideal OP-amp, which of the following is true?
A.
The differential voltage across the input terminals is zero
B.
The current into the input terminals is zero
C.
The current from output terminal is zero
D.
The output resistance is zero
Answer: _________
Question 32:
The OP-amp can amplify
A.
a.c. signals only
B.
d.c. signals only
C.
both a.c. and d.c. signals
D.
neither a.c. nor d.c. signals
Answer: _________
Question 33:
In the differential voltage gain & the common mode voltage gain of a differential amplifier are 48db & 2db respectively, then its common mode rejection ratio is
A.
23dB
B.
25dB
C.
46dB
D.
50dB
Answer: _________
Question 34:
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: _________
Question 35:
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: _________
Question 36:
A voltage follower ___________
A.
has a voltage gain of 1
B.
is noninverting
C.
has no feedback resistor
D.
has all of these
Answer: _________
Question 37:
Hysteresis is desirable in Schmitt-trigger, because
A.
Energy is to be stored/discharged in parasitic capacitances.
B.
Effects of temperature would be compensated.
C.
Devices in the circuit should be allowed time for saturation and desaturation.
D.
It would prevent noise from causing false triggering.
Answer: _________
Question 38:
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: _________
Question 39:
An ideal OP-amp is an ideal
A.
Current controlled Current source
B.
Current controlled voltage source
C.
Voltage controlled voltage source
D.
voltage controlled current source
Answer: _________
Question 40:
The differential voltage gain of a differential amplifier is equal to RC divided by
A.
r' e
B.
$$frac{{{ ext{r}}{{ ext{'}}_{ ext{e}}}}}{2}$$
C.
2r' e
D.
R E
Answer: _________
Question 41:
How many OP-amps are required to implement this equation
A.
2
B.
3
C.
4
D.
1
Answer: _________
Question 42:
A certain noninverting amplifier has Ri of 1 kΩ and Rf of 100 kΩ. The closed-loop voltage gain is
A.
100000
B.
1000
C.
101
D.
100
Answer: _________
Question 43:
The node voltage at the top of the til resistor is closes to ___________
A.
collector supply voltage
B.
zero
C.
emitter supply voltage
D.
tail current times base resistance
Answer: _________
Question 44:
A non inverting closed loop op amp circuit generally has a gain factor
A.
Less than one
B.
Greater than one
C.
Of zero
D.
Equal to one
Answer: _________
Question 45:
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: _________
Question 46:
A differential amplifier ___________
A.
is a part of an Op-amp
B.
has one input and one output
C.
has two outputs
D.
A and B both
Answer: _________
Question 47:
A differential amplifier is invariably used in the input stage of all OP-amps. This is done basically to provide the OP-amps with a very high
A.
CMMR
B.
Bandwidth
C.
Slew rate
D.
Open-loop gain
Answer: _________
Question 48:
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
Answer: _________
Question 49:
The tail current of a differential amplifier is .
A.
half of either collector current
B.
equal to either collector current
C.
two times either collector current
D.
equal to the difference in base currents
Answer: _________
Question 50:
A differential amplifier has a differential gain of 20,000. CMRR = 80dB. The common mode gain is given by
A.
2
B.
1
C.
$$frac{1}{2}$$
D.
0
Answer: _________
Question 51:
The use of negative feedback
A.
reduces the voltage gain of an Op-amp
B.
makes the Op-amp oscillate
C.
makes linear operation possible
D.
A and B both
Answer: _________
Question 52:
In the common mode, ___________
A.
both inputs are grounded
B.
the outputs are connected together
C.
an identical signal appears on both the inputs
D.
the output signal are in-phase
Answer: _________
Question 53:
The two input terminals of an opamp are labeled as
A.
High and low
B.
Positive and negative
C.
Inverting and non inverting
D.
Differential ans non differential
Answer: _________
Question 54:
OP-amp circuits may be cascaded without changing their input output relationships
A.
True
B.
False
Answer: _________
Question 55:
A common mode signal is applied to ___________
A.
the noninverting input
B.
the inverting input
C.
both iputs
D.
top of the tail resistor
Answer: _________
Question 56:
Differential amplifiers are used in
A.
Instrumentation amplifiers
B.
Voltage followers
C.
Voltage regulators
D.
Buffers
Answer: _________
Answer Key
1:
B
Solution: The common mode gain is very low . Key Points: Common Mode Gain: In an operational amplifier (op-amp), common mode gain refers to the gain applied to signals that are present on both the inverting and non-inverting inputs. Purpose: For ideal op-amps, the common mode gain should be extremely low to ensure that the amplifier responds primarily to differential signals (the difference between the inverting and non-inverting inputs). Practical Op-Amps: In real op-amps, although the common mode gain is not zero, it is minimized to enhance performance and accuracy in amplifying differential signals.
2:
C
3:
C
4:
A
5:
D
6:
A
7:
B
8:
C
9:
C
Solution: For an operational amplifier (OP-amp) with negative feedback, the following is true: The output is fed back to the inverting input: Negative feedback involves taking a portion of the output and feeding it back to the inverting input of the OP-amp. This feedback helps stabilize the gain and improve the performance of the OP-amp by reducing distortion and ensuring that the output closely follows the input signal. Negative feedback does not make the output equal to the input, increase the output, or feed the output back to the noninverting input.
10:
D
11:
A
12:
A
13:
B
14:
B
15:
C
Solution: The correct answer is Option C: Summer . Here's why: A digital-to-analog converter (DAC) takes a digital input (like a binary number) and converts it into an analog voltage. Option A: Non-inverter A non-inverting amplifier provides gain but doesn't directly contribute to the conversion process needed in a DAC. Option B: Voltage follower A voltage follower has a gain of 1 and is primarily used for buffering, not for the weighted summing required in DACs. Option C: Summer A summing amplifier (or summer) is crucial in many DAC designs. It takes multiple input voltages and produces an output voltage that is proportional to the weighted sum of the inputs. In a DAC, each digital bit controls a switch that connects a specific voltage (or current) to the summing amplifier's input. The weights are determined by the resistor values, so each bit contributes a different amount to the final output voltage, effectively converting the digital value to its analog equivalent. Option D: Difference amplifier A difference amplifier amplifies the difference between two input voltages and is not directly used in the typical architecture of a DAC. Therefore, the summer amplifier is the core component that performs the digital-to-analog conversion by summing weighted inputs.
16:
A
17:
A
18:
C
19:
D
20:
B
21:
C
22:
D
23:
D
24:
A
25:
A
26:
B
27:
A
28:
D
29:
A
30:
B
Solution: When amplifier stages are connected in parallel, the overall gain is not the product of the individual stage gains. Parallel connection means the input signal is applied to multiple amplifier stages simultaneously, and their outputs are combined. In this case, the gain of each path remains the same and does not multiply. Instead, the currents or voltages at the output may add, depending on how the stages are combined. Overall gain in parallel configuration is determined by other factors such as how the outputs are summed and whether any loading effects are present. In contrast, when amplifier stages are connected in series (cascaded), the overall gain is the product of the individual gains. Therefore, the statement is false for parallel connection.
31:
C
32:
C
Solution: An operational amplifier (OP-amp) is a versatile electronic component designed to amplify a wide range of signals. Both a.c. and d.c. signals : OP-amps are capable of amplifying both alternating current (a.c.) signals and direct current (d.c.) signals. They can be configured in various ways (e.g., as inverting, non-inverting amplifiers) to handle different types of signals and applications. a.c. signals only : This is incorrect because OP-amps are not limited to amplifying only a.c. signals. d.c. signals only : This is also incorrect because OP-amps can amplify both d.c. signals and a.c. signals. neither a.c. nor d.c. signals : This is incorrect because OP-amps are designed to handle both types of signals. Thus, Option C: both a.c. and d.c. signals is the correct answer.
33:
C
34:
B
35:
B
36:
D
37:
C
38:
B
39:
C
40:
C
41:
D
42:
C
Solution: To find the closed-loop voltage gain of a noninverting amplifier, use the formula: Closed-loop voltage gain $$A_{v}$$ = $$1 + frac{R_f}{R_i}$$ Given: - $$R_i$$ (input resistance) = 1 kΩ - $$R_f$$ (feedback resistance) = 100 kΩ Substitute these values into the formula: $$A_{v} = 1 + frac{100000}{1000}$$ $$A_{v} = 1 + 100$$ $$A_{v} = 101$$ Therefore, the closed-loop voltage gain is 101.
43:
B
44:
B
45:
A
46:
D
47:
C
48:
C
49:
C
50:
A
51:
D
52:
C
53:
C
54:
A
55:
C
56:
A