# RF power amplifier

An RF power amplifier
Class C VHF power amplifier based on the transistor MRF317.

An RF power amplifier is a type of electronic amplifier used to convert a low-power radio-frequency signal into a larger signal of significant power, typically for driving the antenna of a transmitter. It is usually optimized to have high efficiency, high output Power(P1dB) compression, good return loss on the input and output, good gain, and optimum heat dissipation.

## Applications

The basic applications of the RF power amplifier include driving to another high power source, driving a transmitting antenna and exciting microwave cavity resonators. Among these applications, driving transmitter antennas is most well known. The transmitter–receivers are used not only for voice and data communication but also for weather sensing (in the form of a RADAR).

## Wideband amplifier design

Impedance transformations over large bandwidth are difficult to realize, thus most wideband amplifiers use 50 Ω output loading. Transistor output power is then limited to

$P_{out} \le \frac{(V_{br} - V_k)^2}{8Z_o}$

$V_{br}$ is defined as the breakdown voltage

$V_k$ is defined as the knee voltage

and typically $Z_o = 50\Omega\,$