Solid-state Power Amplifier (SSPA)

The final stage of the transponder includes a power amplifier such as a TWTA or a transistor solid-state power amplifier (SSPA). SSPAs are tending to replace TWTAs for low-to-medium power requirements due to their better linearity and lower power requirements. The amount of power available for amplification is limited by the power-generation capability of the satellite platform. TWTAs provide output powers of several hundred watts with efficiencies of up to 40–50% with a gain of approximately 55 dB. Solid-state power amplifiers provide output powers of 10 30W with efficiencies of 20–35% with gains of approximately 50 dB.