Transistor Power Amplifiers Unit 2 – Single-ended Power Amplifier
Power gain (Ap) is determined by the ratio of the output power (Po) to the input power (Pi) or
the product of voltage gain (Av) and current gain (Ai).
Ap = Po/Pi = Av x Ai
Power amplifiers have high power gain but low voltage gain.
The peak of the collector-emitter voltage (VCE) may exceed the dc supply voltage (VA) by a
factor of two, as shown in the figure.
When a single-ended power amplifier is designed, VCE must not exceed the transistor
specification.
Amplifiers can be classified as class A, B, or C. The single-ended power amplifier is biased for
continuous current flow (IL), which causes class A operation.
Because output current flows continuously, class A is the least efficient class of amplifier, but it
produces an output signal with practically no amplitude distortion.