An amplifier has a power gain of 12000. If the power gain of the circuit drops by 3dB, the value of Ap is..?

Question

a) 0,

b) 9000,

c) 4000,

d) 6000

Answer 1

6000. In power terms, 3 db is half.

Answer 2

Plug it into the power formula and see what results.

Power dB = 10 log (Po / Pin)

X dB = 10 log (12,000 / 1)

X dB = 40.1

Then,

40.1 dB - 3.0 dB = 37.8 dB

Plug that into the power formula

37.8 dB = 10 log (X / 1)

37.8 dB / 10 = log (X / 1)

3.78 dB = log (X / 1)

3.78 dB = log (X) - log (1)

3.78 dB = log (X) - 0

3.78 dB = log (X)

Solving for X

X = 10^(3.78) = 6025

Answer d) is correct.