Problem in measurement of CGH40010F based Power amplifier

[rd_dinesh]

When I provide DC bias to my circuit, the drain current (which can be seen in the display of my Power supply) is fluctuating a lot and reduces to zero some times in between.
What can be the possible reasons for this kind of behavior and how can I provide stable DC supply to my circuit?

Note: Followed the recommended biasing sequence.

 

[albbg]

You should post the schematic and some specs about your amplifier (frequency, DC point, etc.). In any case it seems that for some reason the stage is not stable. Did you connect a 50ohm load on both input and output ports ?

 

[BigBoss]

Have you ever checked this amplifier with a SA up to very high frequencies? It might oscillate.

 

[vfone]

According to the small signal S-parameters, the gain at 2.4GHz is 12dB, but the gain at 500MHz (lowest measured frequency) is 25dB. So very possible to oscillate.
This is one of the problems of GaN HEMT power transistors, having high gain at low frequencies, when for example LDMOS have pretty flat gain vs frequency.

RF Power GaN on SiC 10W Discrete HEMT 6 GHz | Wolfspeed

Wolfspeed's CGH40010 gallium-nitride HEMT is an unmatched 10W RF power transistor that offers high-efficiency; high-gain; and wide-bandwidth capabilities.

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