Electronics > RF, Microwave, Ham Radio

Always assume 50 ohms Zin and Zout for Power Amp?


I recently came across the following power amp (GRF5504) by Guerrilla RF.
Link to datasheet: https://www.mouser.com/datasheet/2/777/GRF5504DS-1891813.pdf

In the datasheet there is no mention of input or output impedance of this RF PA.
My question is: do we in these cases just assume it's 50 ohms?

There is no matching network in the application schematic which leads me to believe that this part is internally matched to 50ohms.


Well, it is a preliminary datasheet from a company calling themselves "Guerrilla RF", so who can say for sure? More seriously, the datasheet has a page with S-parameters that are very likely referenced to 50 ohm (unless they messed with the VNA just to confuse you) and show matching in the 450-470 MHz range.

Thanks but I don't understand why this information wasn't included in the datasheet's front page, surely it's important? Most manufacturers state "50 ohms internally matched"
Anyways... I sent their applications team an email but I'm awaiting a response...

Sorry, I missed the part where you thought there is no external matching network. No, it is clearly not internally matched but the application circuit shown is presumably matched to 50 ohms (M1, M2 is a simple L-match, output side is a bit more complicated, also provides DC bias). They also have a few more documents showing matching networks tuned for different frequency ranges on their website.

In the 1st  page, under device description: "The device can be tuned over a range of frequencies from around 400 to 500 MHz with typical fraction bandwidths of 3 to 5%". So it definitely requires matching.
I suppose S parameters are not listed only because the DS is preliminary.


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