Electronic Devices and Circuits Multiple Choice Questions on “Effect of Finite Open-Loop gain and Bandwidth on Circuit Performance”.
1. 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.
A. 15Hz and 103 db
B. 30Hz and 103 db
C. 15 Hz and 51.5 db
D. 30 Hz and 51.5 db
2. A single-pole model has __________ db/decade roll-off of the gain.
A. -3 db/decade
B. -6 db/decade
C. -10 db/decade
D. -20 db/decade
Answer: D
Clarification: It is a standard characteristic of a single-pole model.
3. Single-pole model is also known as
A. Frequent pole
B. Stable pole
C. Dominant pole
D. Responsive pole
Answer: C
Clarification: Single-pole model is also called dominant pole.
4. 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
A. 10 kHz
B. 20 kHz
C. 30 kHz
D. 40 kHz
A. 0.1 MHz and -60 db
B. 10 MHz and -60 db
C. 10 MHz and 60 db
D. 1 MHz and 60 db
6. 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?
A. 2π 23.8 kHz
B. 2π 47.6 kHz
C. 2π 71.4 kHz
D. 2π 95.2 kHz
7. 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
A. √(√2+1) f1
B. √(√3-1) f1
C. √(√2-1) f1
D. √(√3+1) f1
8. 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?
A. 1 kHz
B. 10 kHz
C. 100 kHz
D. 1 MHz
Answer: B
Clarification: None
9. 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?
A. 21 kHz
B. 31.5 kHz
C. 42 kHz
D. 52.5 kHz
10. 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?
A. 7.5 MHz
B. 15 MHz
C. 22.5 MHz
D. 30 MHz
Answer: D
Clarification: -R2 ⁄ R1 = -2V⁄V
f3db = 10 MHZ ft = 10 MHZ(2 + 1) = 30 MHZ.