Power Gain Common Emitter Amplifier — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Power Gain (Common Emitter Amplifier) Applies specifically to Bipolar Junction Transistors (BJT) configured in Common Emitter (CE) mode operating in the active region as a small-signal amplifier. Define Power Gain ( A p ) as the ratio of Output Power ( P out ) to Input Power ( P in ). Express Power as Voltage times Current: P = V I . Substitute into ratio: A p = V out I out V in I in . Separate terms: A p = ( V out V in ) ( I out I in ) . Identify terms: V out V in = A v (Voltage Gain) and I out I in ac (Current Gain in CE config). Combine: A p = ac A v . The transistor must be biased in the active region. Applies to small-signal AC analysis. Assumes linear operation without saturation or cutoff clipping. Confusing linear power gain with power gain in decibels ( dB = 10 A p ). Assuming power gain is the square of voltage gain ( A v 2 ), which is only true if input and output impedances are identical (rare in CE amplifiers). Confusing ac (AC current gain) with (common-base current gain).