PA
Understanding PA
Power amplifiers are classified by operating class (A, AB, B, C, D, E, F) based on the conduction angle of the active device. Class A provides the best linearity but lowest efficiency (~25-35%), while switching-mode classes (D, E, F) achieve 60-90% efficiency for constant-envelope signals.
Key PA specifications include output power (P1dB and Psat), power-added efficiency (PAE), gain, linearity (IP3, ACPR), and operating bandwidth. GaN and GaAs are the dominant semiconductor technologies for RF PAs.
Frequently Asked Questions
What is PAE?
Power-Added Efficiency is (Pout - Pin) / PDC, representing the fraction of DC power converted to useful RF output power, accounting for the input drive power.
What is the difference between P1dB and Psat?
P1dB is the output power where gain compresses by 1 dB from the linear value. Psat is the maximum saturated output power, typically 2-3 dB above P1dB.