Help me learn why SGA6486 burns out
I make an dev kit(as shown in SGA6486 datasheet from www.sirenza.com).But when turn on the circuit after 1-3 minutes the SGA6486 burnout,the sch is shown below,the test freq is 433.9MHZ.
why?(I burnout 3 of them)
I apply 6dbm power to input.
At startup it draw current (75mA) but after burnout it draws 400mA! and donot work after that,I biased it with 6VDC.
That IS odd!
Should not be happening.
Are you sure there is a 13 ohm resistor in series between your power supply and the 1 uF capacitor. Make sure it is not 1.3 ohms, for example.
Try disconnecting the FET amp, and power it up with RF source and loads attached, to see if any of the blocking or bypassing capacitors are shorted out. Sometimes people put a tantalum capacitor in backwards, or have a microcracked series capacitor or a solder ball under a component--shorting it out. I would also look at the series resistor with an ohmmeter to see if it shorted out.
I would switch power supplies, in case it was freaking out on me.
If that is ok, I would increase the resistor to maybe 33 ohm, solder a new FET amp in place, and try it out. I would sniff around to see if it were oscillating under my particular load conditions. I would put an oscilloscope on the bias line to see if there were any big ~20 MHz oscillations there.
If that were all ok, and the device lasted long enough, I would drop the resistor down to 13 ohms again and stand back.