RC COUPLED AMPLIFIER

common emitter RC coupled amplifier

      Here R1,R2 and Re are for biasing and stabilization of network.Coupling of one stage to other is obtained by coupling capacitor Cout followed by shunt resistor Rc. Input capacitor Cin couples AC signal voltage to Q1.In the absence of Cin the signal source will be parallel to R2 and bias voltage of base will be affected.Cin allows only AC to the input network.Ce emitter bypass capacitor offer low reactance path to signal.If Ce is absent voltage drop across Re will reduce the voltage available across base emitter, thus reduces the gain.Coupling capacitor Cout block DC voltage from first stage to  the input of second stage while cascading.Hence the DC biasing of next stage is not interfered. Coupling capacitor also called blocking capacitor.
Operation.
            When AC signal is applied to base of Q1 it appears in amplified form across collector load              ( Vout ).This amplified signal is transferred to base of the next stage for further amplification.when input is applied it causes small change in base current resulting in relatively large change in collector current leading to amplification.When input Ib increases collector current Ic increases β times.The increase in Ic with corresponding reduction in collector voltage cause 180 degree phase shift between input and output.

* For single stage amplifier phase shift of input and output is 180 degree.
* For two stage amplifier phase shift of input and output is 360 degree.
*It is widely used in audio frequency operations