Differential Power Amplifier

[Kunna]

Hey,
I was wondering how to design a differential PA, so basically you have two common source amplifiers which are connected to a transformer with a center tap.

How do you do load pull on a differential pair to know the optimum load impedance for the transistor? Do you just use one single transistor instead?

Once you have you optimal impedance, how does the transformer transform the 50 Ohm load?

 

[FvM]

How do you do load pull on a differential pair to know the optimum load impedance for the transistor? Do you just use one single transistor instead?

A real design (either IC or discrete) will have some coupling between both output transistors, also a non-zero power supply impedance. So the impedance of the differential stage is different from the sum of a two individual stages. You'll use a differential load or a balun.