Q. Explain the bandwidth for the curve and the applications of an RC coupled amplifier.

Frequency response curve of an RC coupled amplifier was shown above(prev page). The cut off frequencies f1 and f2 are marked . The difference of the two frequencies i.e the upper cut off frequency f2 and the lower cut off frequency f1 is called the bandwidth.(BW).

Therefore BW = f₂ - f₁.

The BW of an amplifier can also be defined as the range of frequencies from lowest to the highest over which the amplifier delivers sufficient gain. The word sufficient here depends on the applications however...but the common convention is to take the  gain when its dropped by 3 dB.

To decide what BW an audio amplifier requires it again depends mostly on the application. For eg for a telephone circuit, the range is 300hz to 3300 hz, whereas for a hi-fi audio system the BW required is 20 hz - 20 Khz.

Applications : The RC coupled transistor amplifiers are widely used as voltage amplifiers(in the initial stage of public address systems) because of their excellent audio fidelity over a wide range of frequency.However,because of poor impedance matching, this type of coupling is rarely employed in the final stages.