Termination Insensitive Amplifier (TIA)

I have needed some RF/IF amplifiers for my receiver, so I have decided to use the design by Wes Hayward, W7ZOI, and Bob Kopski, K3NHI, originally published in 1999. This amplifier has two main advantages – first, it has a wide bandwidth lacks any tuned circuits, so it is easy to use in a multiband receiver. All that would need to be switched is the input bandpass filter. The second advantage is the rigid 50 Ohm output impedance on the input, no matter what is the output load thanks to the additional emitter follower at the output. That simplifies the receiver construction.

I have built an SMD version of this amplifier as a module that can be used as both the input RF preamp and the IF amplifier in the receiver. My version is not bidirectional – if you need that, you will need to tie two of these side-by-side.

Termination Insensitive Amplifier Schematics

Populated module serving as an IF amplifier after the first ADE-1 mixer.

More pictures and video of a working receiver using these is available here.

If someone is interested, here are design files:

All the passives are 0805 sized and the boards use oversized pads so all components are perfectly hand solderable, without any special tools or magnification.

UPDATE: fixed the Kicad project to be openable with Kicad 4.0.7

 

7 Comments

  • terry lynch commented on November 7, 2017 Reply

    jan, i just ordered some of these . boards from osh-park thank you for sharing this very useful amp. i also ordered some smd bandpass filters (hf) just search for qrp and read down the list. best wishes, terry, ei3iz.

    • Jan commented on November 7, 2017 Reply

      Welcome and enjoy! Hopefully the boards will work fine for you. BTW, if you need to mount them into something, I am just using a double sided tape to stick them down while building. Otherwise hot glue works too.

      I didn’t want to add mounting holes because they would make the boards quite a bit larger.

      Thanks for the tip for the filters, will certainly have a look!

      Regards,

      Jan

  • steve NU0P commented on November 9, 2017 Reply

    I could not load the PCB files into Kicad…Has errors Schematic loaded ok

    • Jan commented on November 9, 2017 Reply

      Hello,

      Sorry about that! What kinds of errors did you get? It could potentially whine about libraries but only standard ones are used (the ones from Github).

      Also make sure you have a really recent version of Kicad, I am using a version compiled in September this year.

    • Jan commented on November 10, 2017 Reply

      Hello Steve,

      I have fixed the file – my Kicad is more recent than the last stable 4.0.7 and it was putting some extra keywords in the board file that the stable version didn’t know how to handle.

      Now it should work fine. Sorry about that!

      Jan

  • steve NU0P commented on November 12, 2017 Reply

    Great…It works now but the Silk Screen layer text is too large but I can fix that I think. I am not an expert on Kicad…Can you tell me if this is a single sided board??? If it is I can make them myself wit this…Steve NU0P

    • Jan commented on November 12, 2017 Reply

      Yes it is single sided.

      However, the silk screen for the part designators is 0.8mm tall already – if you make it smaller or much thinner it may not be manufacturable.

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