Q.Draw the circuit diagram and explain the working of CE amplifier. Also mention any two applications.

A common-emitter amplifier has the emitter common to input and output; the signal is applied to the base and the amplified, phase-inverted output is taken from the collector. …

[!TLDR]

In a CE amplifier the base input controls the collector current ($i_c=\beta i_b$) which develops a large, 180°-phase-shifted output across $R_C$; it gives the highest power gain and is used for audio amplification and in multistage amplifiers.

Circuit: an npn transistor with the emitter as the common terminal. The base bias is set by the voltage divider $R_1,R_2$; $R_C$ is the collector load and $R_E$ with bypass capacitor $C_E$ provides bias stabilisation. Supply $+V_{CC}$ forward biases the base-emitter junction and reverse biases the collector-base junction (active region). The input signal is coupled to the base through $C_1$ and the output taken from the collector through $C_2$.

Working: the AC signal is superimposed on the DC base bias. During the positive half-cycle the forward bias increases, so the base current $i_b$ rises; the collector current rises $\beta$ times, $i_c=\beta i_b$. The increased drop across $R_C$ lowers the collector voltage $V_C=V_{CC}-i_c R_C$, so as the input rises the output falls — a 180° phase reversal. During the negative half-cycle the opposite occurs. The small input signal thus appears greatly amplified at the collector. The emitter resistor $R_E$ stabilises the operating point against temperature and $\beta$ variations, and $C_E$ bypasses $R_E$ for AC so the gain is not reduced. …