61. Decibel is defined in terms of :
(a) Voltage ratio
(b) Current ratio
(c) Power ratio
(d) Any of the above
62. An amplifiers power is changed from 10 watts to 20 watts. The equivalent AB gain will be :
(a) 2 dB
(b) 3 dB
(c) 6 dB
(d) 10 dB
63. A push pull amplifier balances out :
(a) Odd harmonics
(b) Even harmonics
(c) Both a and b
(d) None of these
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Amplifiers » Exercise - 149. The non-linear distortion of an amplifier is D without feedback. The amplifier has an open-loop voltage gain of Av and feedback fraction is mv. With negative voltage feedback, the non-linear distortion will be ....... (a) D (1 + Av mv) (b) D (1 - Av mv) (c) (1 + A m)/D (d) 1 D/(1 + Avmv)- Amplifiers » Exercise - 252. In order to obtain good gain stability in a negative voltage feedback amplifier (Av = voltage gain without feedback ; mv = feedback fraction), ............. (a) Av mv = 1 (b) Av mv >> 1 (c) Av mv < 1 (d) none of the above
- Amplifiers » Exercise - 122. The gain of an amplifier without feedback is 100 db. If a negative feedback of 3 db is applied, the gain of the amplifier will become ........ (a) 101.5 db (b) 300 db (c) 103 db (d) 97 db
- Amplifiers » Exercise - 142. If the input impedance of an amplifier is Zin without feedback, then with negative voltage feedback, its value will be ........... (a) Zin/(1+Avmv) (b) Zin (1 + Av mv) (c) (1+Avmv)/Zin (d) Zin (1 - Av mv)
- Feedback Amplifiers » Exercise - 110. The gain of a negative feedback amplifier is 40 dB. If the attenuation of the feedback path is 50 dB, then the gain of the amplifier without feedback is : (a) 78.92 (b) 146.32 (c) 215.51 (d) 317.23