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Electronics and Communication Engineering - Analog Electronics

Exercise : Analog Electronics - Section 4
46.
If the differential voltage gain and the common mode voltage gain of a differential amplifier are 48 dB and 2 dB respectively, then its common mode rejection ratio is
23 dB
25 dB
46 dB
50 dB
Answer: Option
Explanation:

We know that CMMR =

20 log (CMMR) = 20 log Ad - 20 log Ac = 48 - 2 46 dB.

47.
An npn transistor has a Beta cutoff frequency fβ of 1 MHz, and a common emitter short circuit low frequency current gain β0 of 200. It unity gain frequency fT and the alpha cut off frequency fa2 respectively are
200 MHz, 201 MHz
200 MHz, 199 MHz
199 MHz, 200 MHz
201 MHz, 200 MHz
Answer: Option
Explanation:

.

48.
In figure if the transistor is cut off, the collector voltage is equal to
VCC
0.5 VCC
zero
Answer: Option
Explanation:

Since transistor is cut off, IC = 0 and VC = VCC .

49.
If input frequency is 50 Hz, the frequency of output wave in a full wave diode rectifier circuit is
25 Hz
50 Hz
100 Hz
200 Hz
Answer: Option
Explanation:

There are two output waves for one input wave.

50.
A class A transformer coupled power amplifier is to deliver 10 W output. The power rating of transistor should not be less than
5 W
10 W
20 W
40 W
Answer: Option
Explanation:

Efficiency is 50%. Therefore input is 20 W.

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