I'm having problems with the HMC980 active bias controller and associated amplifier and I need your help.
We've successfully made and tested a few hundred but a couple are giving us problems when switching on at elevated temperatures. Specifically they seem to switch on as expected and work at 'room temperature' and continue to work as the temperature is raised. However they do not seem to switch on at elevated board temperatures. The actual temperature they seem to fail at varies from part to part, one does not seem to switch on at a board temperature of approximately 40degC. Another seems to fail to switch on at a board temperature of approximately 66degC. The board temperature is assumed to be very close to the exposed ground paddle since there are many ground planes in the board to which the paddle is connected and previous experiments with similar devices on the same board have confirmed this assumption.
I attach a few 'scope plots which show that the Vdrain and Vg2 do not seem to switch on at the elevated temperature. All the vertical scales of the 'scope plots should be multiplied by 10, I used x10 probes. The 'scope only had four channels so more than one plot is needed to show the relevant signals.
Please can you suggest how to fix this issue?