Q.Explain with the circuit diagram, the working of RC coupled CE amplifier. Also explain the frequency response.

In an RC coupled CE amplifier the amplified output of one CE stage is passed to the next through a coupling capacitor that transfers AC while blocking DC, and the gain graph is flat only over a mid-frequency band. …

[!TLDR]

An RC-coupled CE amplifier passes the AC output of each stage to the next through a DC-blocking coupling capacitor; the two 180° reversals leave the output in phase, and the frequency response is flat only in the mid band, falling at low and high frequencies.

Circuit: a two-stage CE amplifier using voltage-divider bias. Each stage has bias resistors $R_1,R_2$, collector load $R_C$, and emitter resistor $R_E$ with bypass capacitor $C_E$. The collector of the first stage is connected to the base of the second through a coupling capacitor $C_c$; the input is coupled through $C_1$ and the output through $C_2$.

Working: an AC signal applied to the base of the first stage is amplified and appears at the first collector with a 180° phase reversal. It is passed to the base of the second stage through the coupling capacitor $C_c$, which offers negligible reactance to AC (so it transfers the signal) but blocks DC, so the DC bias of one stage does not disturb the other and each keeps its own operating point. The second stage amplifies the signal again with a further 180° reversal, so the final output is in phase with the input. The overall voltage gain is the product of the stage gains, $A_v=A_{v1}\times A_{v2}$. …