RF Transistor operating conditions

[generator3838]

Hi, I am new to RF amplifier design. I am using CREE CGH40010 for class-AB, Class-C design. Can someone please tell me how can we measure operating condicitons (Idq, Vdq) for any amplifier class?

 

[FvM]

Idq is quiescent drain current, current without RF input. It's about 0 for class B and C, > 0 for class A and AB. There's no thing like Vdq, just Vdd.

 

[generator3838]

Idq is quiescent drain current, current without RF input. It's about 0 for class B and C, > 0 for class A and AB. There's no thing like Vdq, just Vdd.

Thanks for your reply. Is there any formula to calculate Idq for any class? How we actually calculate Idq?

 

[BigBoss]

Thanks for your reply. Is there any formula to calculate Idq for any class? How we actually calculate Idq?

Nonlinear Models of GaN Transistors are quite complex and does easily not allow to calculate Drain Current ( and the others ). So hand calculation is possible but it will not guarantee the exact values. However it looks like classical Ids vs Vgs relationship in CMOS transistors.( similar )

The manufacturer generally mentions the OP and Idq for a specific application circuit that is generally A-Class.
The best way to obtain Ids/Vgs information about these type of transistors is to simulate in a appropriate simulator. Once this information ( e.g. IV Curves ) is obtained, you can decide which Vds and Ids pair is suitable for your purpose. This method is quick and straightforward.

I assume you know well the differences between Classes. If it's so, choose an appropriate OP for those classes and try. Some transistors cannot be suitable for C-Class operating or AB-Class. Refer to manufacturers data.