1. (1) (2) (3) Using HMC980 eval board
Connecting Vdrain in to HMV980 (5V), MMIC Vd not connected. Pulsing Vdig to HMC980 (top traces). Vgate (lower traces)
Gate from HMC980 in three states:
Open circuit -ve goes on then tries to turn up as expected
Connected to MPA -ve charges gate caps the tries to servo up as expected – this amp sequences ok
Connected to PA -ve goes on (rapidly, I have removed gate decoupling) Voltage from HMC980 will not go beyond -0.43V -applying Vgate using power supply: at -0.43V current goes from 0 to 10 mA, this must be what is shutting down the HMC980 -amp works only when a fixed –ve gate is supplied with Vd from HMC980 -HMC data sheet Igate max 4mA!
(2)
Vdig
Vgate
(3)