Working of RC Coupled Amplifier

R.C Coupled Amplifier

The below fig shows a two stage R.C coupled amplifier. Here the first stage is connected to the second stage through the coupling capacitor C_C and resistor R_C. Therefore, this amplifier is called as RC coupled amplifier. The resistor R₁, R₂ from the self bias and R_E form stabilization network. The emitter bypass capacitor offers low reactance path to the signal. This method of coupling is widely used in cascade amplifier stages.

Working:

When the input voltage is applied to the base of the first transistor through a input capacitor C_IN, it appearing the amplified form across its collector load R_C. The output of the first stage is given to the vase of the next stage through coupling capacitor C_C. The second stage does further amplification of the signal.

The coupling capacitor here, helps in blocking the flow of d.c. components from first stage to the second stage. Thus the biasing of the second stage will not disturbed. The coupling capacitor have some reactance and hence there appears some loss of signal voltage due to the drop across this capacitor. This loss caries inversely with the frequency of applied input signal.it may be mentioned here that total gain is less than the product of the gains of individual stages. It is because when a second stage is made to follow the first stage, the effective load resistance of first stage is reduced due to the shunting effect of the input resistance of second stage. This reduces the gain of the stage which is loaded by the next stage.