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

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

[!TLDR]

In a CB amplifier the input at the emitter varies the emitter current, giving a nearly equal collector-current change ($i_c=\alpha i_e$) that develops a large, in-phase output across the collector load; it is used at high frequency and for impedance matching.

Circuit: the transistor is connected with the base as the common terminal. The emitter-base junction is forward biased by $V_{EE}$ and the collector-base junction reverse biased by $V_{CC}$, fixing the active-region operating point. The input signal is applied between emitter and base (through a coupling capacitor) and the output is taken between collector and base across the load resistor $R_L$ (through a coupling capacitor).

Working: the signal adds to the emitter-base bias. During the positive half-cycle the forward bias increases, so the emitter current $i_e$ increases; because $i_c=\alpha i_e$ with $\alpha$ just below 1, the collector current increases almost equally. This collector current flows through the large load $R_L$, and since $R_L$ is large the output voltage $v_o=i_c R_L$ is much greater than the small input voltage — voltage and power amplification. Because emitter and collector currents rise and fall together, the output is in phase with the input (0° phase shift). …