Rf ldmos sd57060 problem

[adnan012]

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.

 

[vfone]

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.

 

[G0HZU]

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

 

[adnan012]

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.

 

[vfone]

**broken link removed**