Olete.in – MCQs, Mock Tests & Government Job Prep | PI (AC/DC) simulation DC Imperfections in Operational Amplifiers

Consider an inverting amplifier with a nominal gain of 1000 constructed from an op amp with an input offset voltage of 3 mV and with output saturation levels of ±10 V. What is (approximately) the peak sine-wave input signal that can be applied without output clipping?

1. 7 mV
2. 10 mV
3. 13 mV
4. 9mV

✅ Correct Answer: 1

Consider an inverting amplifier with a nominal gain of 1000 constructed from an op amp with an input offset voltage of 3 mV and with output saturation levels of ±10 V. If the effect of VOs(input offset voltage) is nulled at room temperature (250C), how large an input can one now apply if the circuit is to operate at a constant temperature?

1. 8.5 mV
2. 9 mV
3. 9.5 mV
4. 10 mV

✅ Correct Answer: 4

Consider an inverting amplifier with a nominal gain of 1000 constructed from an op amp with an input offset voltage of 3 mV and with output saturation levels of ±10 V. If the effect of VOs(input offset voltage) is nulled at room temperature (250C). The circuit is to operate at a temperature in the range 0°C to 75°C and the temperature coefficient of VOS is 10 μV/°C?

1. 8.5 mV
2. 9 mV
3. 9.5 mV
4. 10 mV

✅ Correct Answer: 3

One of the DC imperfections of the amplifiers are dc offset voltage which is

1. Existence of output signal even when the common mode signal is zero
2. Existence of common mode signal causing zero output signal
3. Existence of output signal even when the differential signal is zero
4. Existence of differential signal causing zero output signal

✅ Correct Answer: 3

Consider an inverting amplifier circuit designed using an op amp and two resistors, R1 = 10 kΩ and R2 = 1 MΩ. If the op amp is specified to have an input bias current of 100 nA and an input offset current of 10 nA, find the output dc offset voltage resulting.

1. 0.1 mV
2. 1 mV
3. 10 mV
4. 100 mV

✅ Correct Answer: 4

Consider a Miller integrator with a time constant of 1ms and an input resistance of 10 kΩ. Let the op amp have VOS (offset voltage) = 2 mV and output saturation voltages of ±12 V. Assuming that when the power supply is turned on the capacitor voltage is zero, how long does it take for the amplifier to saturate?

1. 3s
2. 6s
3. 9s
4. 12s

✅ Correct Answer: 2

Consider a Miller integrator with a time constant of 1ms and an input resistance of 10 kΩ. Let the op amp have VOS (offset voltage) = 2 mV and output saturation voltages of ±12 V. Select the largest possible value for a feedback resistor RF so that at least ±10 V of output signal swing remains available.

1. 10 kΩ
2. 100 kΩ
3. 1 MΩ
4. 10 MΩ

✅ Correct Answer: 4

Consider a Miller integrator with a time constant of 1ms and an input resistance of 10 kΩ. Let the op amp have VOS (offset voltage) = 2 mV and output saturation voltages of ±12 V. What is the corner frequency of the resulting STC network?

1. 1 Hz
2. 0.16 Hz
3. 0.33 Hz
4. 0.5 Hz

✅ Correct Answer: 2

An internally compensated op amp is specified to have an open-loop dc gain of 106 dB and a unity gain bandwidth of 3 MHz. Find fb and the open-loop gain at fb.

1. 15Hz and 103 db
2. 30Hz and 103 db
3. 15 Hz and 51.5 db
4. 30 Hz and 51.5 db

✅ Correct Answer: 1

A single-pole model has __________ db/decade roll-off of the gain.

1. -3 db/decade
2. -6 db/decade
3. -10 db/decade
4. -20 db/decade

✅ Correct Answer: 4

Single-pole model is also known as

1. Frequent pole
2. Stable pole
3. Dominant pole
4. Responsive pole

✅ Correct Answer: 3

An op amp having a 106-dB gain at dc and a single-pole frequency response with ft = 2 MHz is used to design a non-inverting amplifier with nominal dc gain of 100. The 3-dB frequency of the closed-loop gain is

1. 10 kHz
2. 20 kHz
3. 30 kHz
4. 40 kHz

✅ Correct Answer: 2

An internally compensated op amp has a dc open-loop gain of 106 V/V and an AC open-loop gain of 40 dB at 10 kHz. Estimate its gain–bandwidth product and its expected gain at 1 kHz.

1. 0.1 MHz and -60 db
2. 10 MHz and -60 db
3. 10 MHz and 60 db
4. 1 MHz and 60 db

✅ Correct Answer: 4

An inverting amplifier with nominal gain of −20 V/V employs an op amp having a dc gain of 104 and a unity-gain frequency of 106 Hz. What is the 3-dB frequency f3dB of the closed-loop amplifier?

1. 2π 23.8 kHz
2. 2π 47.6 kHz
3. 2π 71.4 kHz
4. 2π 95.2 kHz

✅ Correct Answer: 2

cascading two identical amplifier stages, each having a low-pass STC frequency response with a 3dB frequency f1, results in an overall amplifier with a 3dB frequency given by

1. √(√2+1) f1
2. √(√3-1) f1
3. √(√2-1) f1
4. √(√3+1) f1

✅ Correct Answer: 3

Find the ft required for internally compensated op amps to be used in the implementation of the closed loop amplifiers with dc gain of +100 V/V and 3db bandwidth of 100kHz?

1. 1 kHz
2. 10 kHz
3. 100 kHz
4. 1 MHz

✅ Correct Answer: 2

A particular op amp, characterized by a gain–bandwidth product of 20 MHz, is operated with a closed-loop gain of +100 V/V. What 3-dB bandwidth results? At what frequency does the closed-loop amplifier exhibit a −6° phase shift?

1. 21 kHz
2. 31.5 kHz
3. 42 kHz
4. 52.5 kHz

✅ Correct Answer: 1

Find the ft required for internally compensated op amps to be used in the implementation of the closed loop amplifiers with dc gain of -2 V/V and 3db bandwidth of 10 MHz?

1. 7.5 MHz
2. 15 MHz
3. 22.5 MHz
4. 30 MHz

✅ Correct Answer: 4

Single-pole model is also known as

1. Frequent pole
2. Stable pole
3. Dominant pole
4. Responsive pole

✅ Correct Answer: 3

An inverting amplifier with nominal gain of −20 V/V employs an op amp having a dc gain of 104 and a unity-gain frequency of 106 Hz. What is the 3-dB frequency f3dB of the closed-loop amplifier?

1. 2π 23.8 kHz
2. 2π 47.6 kHz
3. 2π 71.4 kHz
4. 2π 95.2 kHz

✅ Correct Answer: 2

cascading two identical amplifier stages, each having a low-pass STC frequency response with a 3dB frequency f1, results in an overall amplifier with a 3dB frequency given by

1. √(√2+1) f1
2. √(√3-1) f1
3. √(√2-1) f1
4. √(√3+1) f1

✅ Correct Answer: 3

A particular op amp, characterized by a gain–bandwidth product of 20 MHz, is operated with a closed-loop gain of +100 V/V. What 3-dB bandwidth results? At what frequency does the closed-loop amplifier exhibit a −6° phase shift?

1. 1 kHz
2. 10 kHz
3. 100 kHz
4. 1 MHz

✅ Correct Answer: 2

Slew rate of an amplifier is defined as

1. Minimum rate of change of the output possible in a real operational amplifier
2. Maximum rate of change of the output possible in a real operational amplifier
3. Average rate of change of the output possible in a real operational amplifier
4. Ratio of the maximum and the average rate of change of the output in a real amplifier

✅ Correct Answer: 2

Determine the slew rate of the amplifier having full power bandwidth f0 and the rated output voltage as V0. Given that the input signal is of sinusoidal nature.

1. 2πf0 V0
2. V0 / 2πf0
3. V0 / f0
4. f0 V0

✅ Correct Answer: 1

The units of the full power bandwidth is

1. Watt
2. Joule
3. Seconds
4. Hertz

✅ Correct Answer: 4

For NMOS transistor which of the following is not true?

1. The substrate is of p-type semiconductor
2. Inversion layer or induced channel is of n type
3. Threshold voltage is negative
4. None of the mentioned

✅ Correct Answer: 3

Process transconductance parameter is directly proportional to

1. Electron mobility only
2. (Electron mobility)-1 only
3. Oxide capacitance only
4. Product of oxide capacitance and electron mobility

✅ Correct Answer: 4

The SI Units of the Process transconductance Parameter (k’) is

1. V2/A
2. A/V2
3. V/A
4. A/V

✅ Correct Answer: 2

Aspect ratio of the MOSFET has the units of

1. No units
2. m
3. m2
4. m-1

✅ Correct Answer: 1

The MOSFET transconductance parameter is the product of

1. Process transconductance and inverse of aspect ratio
2. Inverse of Process transconductance and aspect ratio
3. Inverse of Process transconductance and inverse of aspect ratio
4. Process transconductance and aspect ratio

✅ Correct Answer: 4