Configurable, variable gain, voltage/current amplifier

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I work with a lot of analog signals from different sources/sensors and every time I have to make something useful with it (conversion, multiplication, viewing it on an oscilloscope, etc), the signal is either too small to use, too noisy or too big.

Especially for debugging purposes. Bread-boarding an op-amp every time I need to boost the signal or a current to voltage convertor is really starting to annoy me.

From this frustration came the AmpFarmer (notice that I have not abandoned my "brand").

Features (for now):

- 3.3v to 26v (+/- 12v) Supply voltage single supply or not

- 145 MHz GBWP, 7nV/Sqrt(Hz), low bias, etc (see opamp datasheet)

- User selectable gain from 1 to 9000

- can be configured as a current to voltage converter (transconductance amplifier) with gains of 10, 100 and 1000

- can be configured as a inverting or non-inverting amp

- AC/DC input selection

- footprints for BNC, SMA and header pins for the input and output.

Any other ideas are welcome.


Eagle Schematic v0.1

sch - 341.42 kB - 10/20/2016 at 16:18


  • 1 × AD8065 Video, Graphics and Imaging ICs / Amplifiers
  • 2 × Rotary switch
  • 1 × BNC Connector Connectors and Accessories / RF and Coaxial Connectors
  • 1 × Misc Components

  • Go big or go... to china?

    Radu Constantin02/21/2017 at 17:04 0 comments

    I've decided that if I will make this board I will do it right.

    The new boards and the stencils are here from China and they look great. I will start assembling them soon.

    Also... how does a 2nd order Sallen-Key filter, with variable cutoff frequency sound? Both LP and HP. (BP and BS with 2 boards)

  • To Tindie or not to Tindie?

    Radu Constantin10/20/2016 at 16:36 2 comments

    My colleagues proposed that I should try to sell this device on Tindie. The costs would be about 17 Euros per board (19$). I've never really liked Tindie.

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shane ormonde wrote 12/25/2016 at 02:15 point

The main thing I'd like to see would be get rid of the BNC connectors and use screw terminal connectors so you can hook up whatever wires you want. Using a BNC connector would restrict the usefulness of something like this for me anyways

  Are you sure? yes | no

Radu Constantin wrote 01/04/2017 at 18:17 point

The board has footprints for BNCs, SMAs and 4 pin single line headers. You can solder whichever you want. I chose BNC because it was easier to connect to the analyzer. Can you give me a reference for the screw terminals?

  Are you sure? yes | no

shaneormonde wrote 12/20/2016 at 17:46 point

You should totally sell this on Tindie. The amount of times i've had to quickly put together an op-amp circuit on a breadboard to amplify some sensor signal is crazy high. This would save all that hassle.

  Are you sure? yes | no

Radu Constantin wrote 12/21/2016 at 17:35 point

I know that feeling. I'm working on a new version of the board. Can you think of any other features to add?

  Are you sure? yes | no

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