GaAs MMIC power Amp on/off

[7rots51]

I use a GaAs PA MMIC (class A)that consumes 1.2A current and gives 3W RF and wastes 12W as heat.

My RF transmitter is 0.2sec ON and 0.8sec OFF.
For reducing heat can I turn on/off(switching) the supply of GaAs PA MMIC? Is this a good way or this method is harmful for GaAs PA MMIC?

 

[biff44]

You have to trade off the situation.

Running a GaAs junction hot for a long time will accelerate failure, probably due to metal migration.

Turning the FET on and off VERY frequently will temperature cycle the part to the extreme, and cause some sort of microcracking eventually.

If you only care about Heat, how about turning it part way off. Like go from 12 watts to 1 watt. That will keep the temperature extremes smaller, and allow more temperature cycles.

Of course, if you only transmit for 100 mS in every 10 minutes, I would turn it completely off.

 

[7rots51]

I have to send every second but my problem is heat.

 

[BigBoss]

Instead of turning-off your PA, you may alo use an attenuator to decrease your signal to very low level.In this case your PA will consume some power but only little ( I assume your RF power is set to zero)
That can be an alternative..

 

[kspalla]

I used this technique to increase the DC power efficiency. Per example in radar the transmission is only 10% and rest is in receive mode.
You can turn off the device for this kind application.
The problem is damaging the MMIC under no DC power but RF Power.
To avoid it, you need to be very careful in controlling the VDD per say. VDD pulse should cover the RF puse.