Electronic Devices and Circuits Multiple Choice Questions on “Frequency Response – 1”.
(Q.1-Q.3) A parallel resonant circuit has a resistance of 2k ohm and half power frequencies of 86 kHz and 90 kHz.
1. The value of capacitor is
A. 6 µF
B. 20 nF
C. 2 nF
D. 60 µF
Answer: B
Clarification: BW = 2p(90-86)k = 1/RC or C = 19.89 nF.
2. The value of inductor is
A. 4.3 mH
B. 43 mH
C. 0.16 mH
D. 1.6 mH
Answer: C
Clarification: w = (86 + 90)k/2 = 88 = (1/LC.(0.5) or L = 0.16 mH.
3. The quality factor is
A. 22
B. 100
C. 48
D. 200
Answer: A
Clarification: Q = w/BW = 176pK/8pk = 22.
(Q.4-Q.5) A parallel resonant circuit has a midband admittance of 25 X 10(-3) S, quality factor of 80 and a resonant frequency of 200 krad s.
4. The value of R (in ohm) is
A. 40
B. 56.57
C. 80
D. 28.28
Answer: A
Clarification: At mid-band frequency Y = 1/R or R = 1000/25 or 40 ohm.
5. The value of C is
A. 2 µF
B. 28.1 µF
C. 10 µF
D. 14.14 µF
Answer: C
Clarification: Q = wRC or C = 80/(200 x 1000 x 40) or 10 µF.
6. A parallel RLC circuit has R 1 k and C 1 F. The quality factor at resonance is 200. The value of inductor is
A. 35.4 H
B. 25 H
C. 17.7 H
D. 50 H
Answer: B
Clarification: Use Q = R (L/C.0.5.
7. A parallel circuit has R = 1k ohm , C = 50 µF and L = 10mH. The quality factor at resonance is
A. 100
B. 90.86
C. 70.7
D. None of the above
Answer: C
Clarification: Use Q = R (L/C.0.5.
8. A series resonant circuit has L = 1 mH and C = 10 F. The required R (in ohm) for the BW = 15 9 . Hz is
A. 0.1
B. 0.2
C. 0.0159
D. 500
Answer: A
Clarification: Use BW = R/L.
9. For the RLC parallel resonant circuit when R = 8k, L = 40 mH and C = 0.25 F, the quality factor
Q is
A. 40
B. 20
C. 30
D. 10
Answer: B
Clarification: use Q = R (C/L)0.5.
10. A series resonant circuit has an inductor L = 10 mH. The resonant frequency w = 10^6 rad/s and bandwidth is BW = 103 rad/s. The value of R and C will be
A. 100 F, 10 ohm
B. 100 pF, 10 ohm
C. 100 pF, 10 Mega-ohm
D. 100 µF, 10 Meg-ohm
Answer: B
Clarification: Use wxw = 1/LC and BW = R/L.