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Rf ldmos sd57060 problem

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adnan012

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I am using SD57060 in my project. PA is designed to give 10-30 W at 100MHz.
SD57060 was sold on prototype board by technician. The problem is that Idq is 1.5A at VGS =0. Idq increases when Vgs is increased from 0 to 0.7V. PA can still provide 7-11W power (i did not tried for more power as Idq increase.) VDS is 12-13.6V. My question is that if the LDMOS gate has been damaged by ESD.
 

I don't know if the transistor was damaged by ESD, but I think is dead. There is one possibility that one of the drain to ground capacitors to get some leakage currents. These should be high-quality ceramic capacitors. Check them, and if they are ok definitely the transistor is damaged.
 

Have you considered the possibility that your design could be unstable and the device is oscillating?
 
Thanks for reply.

I was using a variable voltage linear power supply. I noticed that when the supply id switched on or switched off, it produces high transient voltages (50 plus volts ) for few milliseconds. I verified it on oscilloscope.

I will purchase ceramic capacitors from Digikey or Mouser. What type ceramic capacitors should i use?.

---------- Post added at 07:41 ---------- Previous post was at 07:38 ----------

I followed Phillips application notes of RF power amplifier design and verified the design using ADS simulation.
 

**broken link removed**
 

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