In the datasheet Sirenza specifies that this transistor passes ESD at 500V, but in this Reliability Qualification Report is specified that fails below 250V.
Do you have stable application? Have you terminated the input and output ports correctly? It is possible that after biasing the transistor, it starts to oscillate and burns right away. Also Drain bias has to be applied first and the gate bias after that (in that particular LDMOS transistor) In case you would have GaAs FET, you should apply first the negative gate voltage and after that the drain bias.
Yes, i think you need to redesign your matching networks.
Insulator is good idea because it protects your PA (usually from the Standing wave) if something happend with conection with antenna.
mm , Vfone , i have used the load pull data to design the input and output impedance , and followed the recommendations , but in the datasheet they mentioned not to apply the bias till the PA is terminated
mm , Vfone , i have used the load pull data to design the input and output impedance , and followed the recommendations , but in the datasheet they mentioned not to apply the bias till the PA is terminated
Yes, that's right..
The PA's can "potentially" oscillate while they are not connected or terminated with a proper load even the matching circuits are connected. Because matching circuit input impedance which is seen by PA will be different than when the its output is terminated with load.If the reflection coefficient that is seen by PA transistor is high enough, the reflected voltage will increase till the power transistor is dead.
For instance if the reflection coefficient is around 1, the VCE voltage acrossing C-E junction will be doubled, if PA works in Class A, this may vary 0-4Vcc ( theoritically,depending on reflection phase etc.).And also, it should be considered the reflection current from non-proper loads.
Output circuit must be double terminated for stabiliy..
Also, input termination will influence the overall stability ( less than output). And finally , both input and output should be terminated by proper impedances for an exact stability.
Otherwise, the PA will "probably" oscillate and destroy the power transistor.