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Analysis of bandwidth of an amplifier and output power signal

An audio amplifier has the following frequency response (transfer function):
At 20 Hz, gain = 30 dB.
At 60 Hz, gain = 37 dB.
At 120 Hz, gain = 40 dB.
At 10,000 Hz, gain = 40 dB.
At 12,000 Hz, gain = 37 dB.
At 16,000 Hz, gain = 30 dB.
The gain of the amplifier is constant from 120 Hz to 10 kHz at 40 dB.

a. What is the 3 dB bandwidth of the amplifier, in Hz?

b. What is the 10 dB bandwidth of the amplifier in Hz?

c. A 1 kHz sine wave signal with a power level -10 dBm is applied to the input of the amplifier. What is the power at the amplifier output in dBW?

d. A 12 kHz sine wave signal with a power level -25 dBm is applied to the input of the amplifier. What is the power at the amplifier output in dBm?

Solution Preview

(A) The 3 dB bandwidth is the frequency range where the gain drops by 3 dB from its maximum value (in this case 40 dB). Thus we should look for the frequencies in this case where the gain drops to 37 dB. Gain drops to 37 dB at frequencies of 60 Hz and 12,000 (= 12 kHz)

Thus the 3 ...

Solution Summary

The solution explains how you can calculate different bandwidths of a described amplifier. Furthermore it answers the power of an amplifier output.

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