rf transistor failure

[prd]

type of rf transistor failure

Dear rf guru,

I'm testing rf pa design, based on BFG425W. But after I test the circuit, the transistor would be destroyed and can not perform signal amplifiaction.

My circuit is 3V supply, Ic 10mA, fixed bias. with AC coupling from source and load.
I try input signal with -20dBm, -10dBm, -5dBm.

Are there any things that I should be carefule when test PA circuit ?

prd

 

[Borber]

transistor failure

I suspect that failure happens when you switch off supply voltage. At this instant transistor maximum ratings are exceeded. Check bias circuit, check the behaviour of your power supply when you switch it off.

 

[vfone]

checking transistor failure

BGW425W can get +12dBm linear output power with a power gain of 17dB. That means could support -5dBm at the input without problems (if the bias is correct).
Try to match the output for maximum power and not for maximum gain, and also check for stability at a large frequency range.

 

[flyhigh]

Hi,

you should also check that the grounding of sources is good.

flyhigh