Transistor Power Gain Common Emitter — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Transistor Power Gain (Common Emitter) Applies to NPN or PNP transistors operating in the active region specifically for the Common Emitter (CE) configuration. Define Power Gain as the ratio of change in output power to change in input power (A p = P out / P in) Substitute power formula P = I 2 R: A p = (I c 2 R L) / (I b 2 R i) Identify the current gain Beta as the ratio of collector current to base current (Beta = I c / I b) Combine to get A p = Beta 2 (R L / R i) Transistor must be in active region Small signal approximation is assumed Frequency must be low enough that parasitic capacitances are negligible Confusing Beta (CE) with Alpha (CB gain) Assuming power gain is simply Beta without accounting for the resistance ratio Applying the formula when the transistor is in saturation or cutoff regions