Common gate wideband RF amplifiers

[ProphetM]

I just built the VHF FM LNA circuit this evening but I tweaked it for 50 ohm ports rather than the expected 75 ohm. This makes it easier for me to measure as all my test gear here has 50 ohm ports.

See below for the simulation (based on my s-parameter data of the CPH3910 and some simple circuit models for the R, L and C components) and this is compared to a measurement of the built circuit using the VNA. I think if I had measured the inductors on the VNA and I had modelled the circuit strays better in the simulation the agreement would have been closer. Even so, there will be some spread due to component tolerances.

This does at least show that I can measure s-parameters of SMD components quite well!

I'll have a go at measuring the noise figure and the signal handling tomorrow.

Hi G0HZU,

Please do you still have the schematic for this amplifier?
I've tried designing a "wideband" amplifier from s-parameters with no luck.

Maybe the solution is to do wideband matching : more than 2 reactive elements ?


Thanks

[LM21]

Interesting. It is nice to build using basic components, but do you know that there are low noise MW ICs with large frequency range.

I once had a nice analog FM tuner/receiver made with RCA 40822 dual gate mosfets. It had a low noise figure and fets were soft(easily overloaded) that I could hear many narrow band FM transmitters (Taxis), and  aircraft AM with it. So I  am not very quick to trust fets as LNAs.