Doherty power amplifier

Hi,
Trying to design a doherty power amplifier little confusion on choosing bias point for class AB and class C power amplifier.Do we choose the bias point based on the vgs and Id curve obtained from the curve tracer in ADS?

Of course you should know the bias point for both C-Class and AB-Class.In order to decide these OPs, you have to know DC IV Characteristics of the Transistors.

I understand that but I am having confusion choosing the bias point. while reading a few papers I saw a different process for chooisng the bias I attached the figure for two approches and would like to know which is correct. Thanks.

Hi,

I am trying to design a Doherty power amplifier,can anyone explain how to design the offset lines. I used (z=50,90 degree) and (z=35.35, 90 degree) transmission lines as combiner circuit to 50 ohm load.I am not able to obtain desired efficiency at back off. Please help.



Thanks.