How To Match RF Power Amp?

[that_rf_guy]

Hi all,

I'm in a bit of a pickle wrapping my head around the matching of a CGHV59070F power amp (link here). The manufacturer states that it is "internally matched", but given the price tag I'd like to verify that this means it should see 50 Ohms on the input and output. The example PCB layout on page 5 of the datasheet (link here) seems to show a stepped transmission line on the output of the package. There are also a number of small rectangular pads on the side of the stepped transmission line - if anyone knows what their purpose is, please chime in, I've been stumped with them as well for some time!

[David Hess]

At high power and low voltage, the low output impedance would be difficult to match externally, so internal matching raises the output impedance, but not all the way to 50 ohms in this case so an external matching network is still required for maximum output power.

[that_rf_guy]

Thank you David, that was what I assumed given the topology shown on the example circuit. However MACOM has gotten back to me and claims that they do not supply load-pull data as it is in fact internally matched to 50 Ohms. Curious as to how they pulled that off inside.

[mtwieg]

I looked at the S2P file, at ~5GHz |S11| is around -6dB, |S22| is around -3dB, which is fairly good. But that might be based on their reference layout which has some necessary features in it to improve the matching.