Small signal s-parameter measurements were carried out on the fully assembled amplifier at package base temperatures of -33°C, 25°C and 85°C. These measurements were carried out under CW conditions, and the results are shown in Figure 5. The s-parameter data demonstrates that the final amplifier has a small signal gain of around 11 dB across the band, which varies by around ±1.5 dB over temperature. The input return loss is hardly affected by temperature and is better than 15 dB across the band. The output return loss is nominally around 9.2 dB and varies by around ±1 dB over temperature.
Large signal measurements were also carried out over temperature. These measurements were performed under pulsed conditions and utilized the on-board drain switching circuit, which provided a turn-on time of just 20ns. The duty cycle was 10% and the pulse width was 500µs. The RF envelope during the 500µs pulse is shown in Figure 6 for the amplifier running at 3 dB compression at mid-band. Clean, fast edges were evident, and there is very little power drop across the pulse period.