A high performance RF power amplifier with protection against load mismatches

A high performance power amplifier is presented which includes a protection circuitry against load impedance variations. Load mismatches produce peak voltages on the power transistor collector that give rise to breakdown conditions and hence to permanent faults. The protection circuitry is based on a feedback loop that acts on the amplifier gain to limit the overdrive of the output transistor. A monolithic power amplifier for 1.8-GHz DCS-PCS applications was integrated in a silicon bipolar technology with a 4.3-V breakdown voltage. The amplifier delivers a 33-dBm output power with 51% power-added efficiency and 33-dB gain at a nominal 3-V supply voltage. Standing wave ratio was tested up to 20:1 for all phases with a supply voltage up to 3.8 V without damage to the device.