how to perform output matching for a power amplifier.

[hunas2127]

As shown in the figure above, I connected four transistors in parallel at the output stage to increase the output power.
ZLOPT is the optimum load impedance obtained from a load-pull simulation of a single transistor.
I'm planning to match the impedance using the method shown in the diagram below.

1. Should I match 50 ohms to ZLOPT? Or since there are four transistors connected in parallel, should I match 50 ohms to ZLOPT/4?
2. I understand that I can use a series inductor for matching,
   but I don't know how to convert this into a series transmission line.
   For example, if I have a 100 pH inductor, how can I replace this with an equivalent transmission line?

 

[BradtheRad]

To perform impedance matching, we take a waveform of V amplitude and A Amperes available at output...
and convert it into a combination of volts and Amperes which is optimized for use in the following stage. Thus we maximize power (Watts) from one stage to the next.

It appears you turn on positive polarity during one-half of a cycle, while negative is shut off. Then vice-versa during the second half of the cycle. At any moment two parallel transistors conduct.

Thus you might say your impedance is Z/2, that is, if you're getting double the Amperes.

 

[BigBoss]

Optimum Load Impedance should be a common impedance for combined amplifiers not individually.
In order to realize an inductor, think about a short circuited transmission line with a length smaller than lambda/4.That equation will give you an insight.

 

[dick_freebird]

Load pull jig? Or its simulation equivalent? Easier
to find than to figure, presuming models are good.

Doubt that the amplifier gets to decide the system
"standard impedance" (50 ohms? Something else?)
and if other than 50, probably some impedance
transforming network (see this a lot w/ low voltage
PAs trying to make power, and any switching-class
PA (whose Zout goes near to zero when on)?