Pulsed vs. CW power performance of InGaP/GaAs HBTs

Load-pull power and waveform measurements were performed on C-band InGaP/GaAs heterojunction bipolar transistors of various sizes. In general, pulsed output power was found to be 2-4dB higher than CW output power. Based on the measured dynamic load lines, the higher output power can be attributed to higher peak current and higher breakdown voltage under pulsed conditions. From the measured harmonic contents, pulsed operation was also found to be more linear than CW operation, probably due to the absence of thermally induced weak nonlinearity under pulsed conditions.