Millimetrica designs controllers and integrated linear power supply for sophisticated and delicate RF devices, such GaAs FETs, power GaAs FETs, PINs, requiring precise voltage/current control and protection for safety use.
Power GaAs Fets and PINs Power Supply protection
Power GaAs FETs are generally quite delicate in term of voltages handling such the drain current and gain are directly depending from the negative gate voltage variations. If the negative voltage is missing the drain current goes to its max limit and the device can be destroyed in a few nS.
Millimetrica has developed a special protection circuit, based on single or dual MosFets switch applicable to any power supply with the funtion to shut down the positive voltage in case of negative voltage lost. The circuit is also able to delay the positive voltage when the power device is switched on and to delay the the negative when switched off.
This circuit can be used with high power RF PIN switch requiring dual voltges, to prevent failures when the RF pattern is applied.
Picture 1 shows how the circuits controls a PIN diode switch requiring -28/+5 VDC (-28V-Yellow traces/ +5 -blue traces) and the delay time. The positive voltage cannot rise if the negative is missed. If the negative slow down, the positive will be shut immediately, after a min .treshold.