The present disclosure generally relates to semiconductor structures and, more particularly, to a fully depleted silicon on insulator power amplifier with unique biases and voltage standing wave ratio protection and methods of manufacture. The structure includes a pseudo-differential common source amplifier; first stage cascode devices connected to the pseudo-differential common source amplifier and protecting the pseudo-differential common source amplifier from an over stress; second stage cascode devices connected to the first stage cascode devices and providing differential outputs; and at least one loop receiving the differential outputs from the second stage cascode devices and feeding back the differential outputs to the second stage cascode devices.