Limiting the Output Power of Rugged GaN LNAs

Rugged GaN HEMT low-noise amplifiers are well established, but the common concept of achieving ruggedness by applying the gate supply voltage through a high ohmic resistance might not be sufficient in addition to control the maximum output power. This paper shifts the focus to the protection of subsequent stages and proposes a circuit concept based on an output attenuator and an adaptive drain supply. It is shown that the concept implementation provides an attenuation of up to 28dB under input overdrive condition while leaving small-signal noise Figure unaffected.