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DC Imperfections in Operational Amplifiers
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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. What is (approximately) the peak sine-wave input signal that can be applied without output clipping?
7 mV
10 mV
13 mV
9mV
2. 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?
8.5 mV
9 mV
9.5 mV
10 mV
3. 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?
8.5 mV
9 mV
9.5 mV
10 mV
4. One of the DC imperfections of the amplifiers are dc offset voltage which is
Existence of output signal even when the common mode signal is zero
Existence of common mode signal causing zero output signal
Existence of output signal even when the differential signal is zero
Existence of differential signal causing zero output signal
5. 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.
0.1 mV
1 mV
10 mV
100 mV
6. 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?
3s
6s
9s
12s
7. 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.
10 kΩ
100 kΩ
1 MΩ
10 MΩ
8. 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 Hz
0.16 Hz
0.33 Hz
0.5 Hz
9. 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.
15Hz and 103 db
30Hz and 103 db
15 Hz and 51.5 db
30 Hz and 51.5 db
10. A single-pole model has __________ db/decade roll-off of the gain.
-3 db/decade
-6 db/decade
-10 db/decade
-20 db/decade
11. Single-pole model is also known as
Frequent pole
Stable pole
Dominant pole
Responsive pole
12. 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
10 kHz
20 kHz
30 kHz
40 kHz
13. 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.
0.1 MHz and -60 db
10 MHz and -60 db
10 MHz and 60 db
1 MHz and 60 db
14. 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?
2π 23.8 kHz
2π 47.6 kHz
2π 71.4 kHz
2π 95.2 kHz
15. 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
√(√2+1) f1
√(√3-1) f1
√(√2-1) f1
√(√3+1) f1
16. 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 kHz
10 kHz
100 kHz
1 MHz
17. 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?
21 kHz
31.5 kHz
42 kHz
52.5 kHz
18. 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?
7.5 MHz
15 MHz
22.5 MHz
30 MHz
19. Single-pole model is also known as
Frequent pole
Stable pole
Dominant pole
Responsive pole
20. 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?
2π 23.8 kHz
2π 47.6 kHz
2π 71.4 kHz
2π 95.2 kHz
21. 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
√(√2+1) f1
√(√3-1) f1
√(√2-1) f1
√(√3+1) f1
22. 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 kHz
10 kHz
100 kHz
1 MHz
23. Slew rate of an amplifier is defined as
Minimum rate of change of the output possible in a real operational amplifier
Maximum rate of change of the output possible in a real operational amplifier
Average rate of change of the output possible in a real operational amplifier
Ratio of the maximum and the average rate of change of the output in a real amplifier
24. 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.
2πf0 V0
V0 / 2πf0
V0 / f0
f0 V0
25. The units of the full power bandwidth is
Watt
Joule
Seconds
Hertz
26. For NMOS transistor which of the following is not true?
The substrate is of p-type semiconductor
Inversion layer or induced channel is of n type
Threshold voltage is negative
None of the mentioned
27. Process transconductance parameter is directly proportional to
Electron mobility only
(Electron mobility)-1 only
Oxide capacitance only
Product of oxide capacitance and electron mobility
28. The SI Units of the Process transconductance Parameter (k’) is
V2/A
A/V2
V/A
A/V
29. Aspect ratio of the MOSFET has the units of
No units
m
m2
m-1
30. The MOSFET transconductance parameter is the product of
Process transconductance and inverse of aspect ratio
Inverse of Process transconductance and aspect ratio
Inverse of Process transconductance and inverse of aspect ratio
Process transconductance and aspect ratio
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