Analog Basics: Inverter/Amplifier (publ. 2025-01-27)

I built an inverter, adding it on to the breadboard with the integrator I built last week.

=> breadboard with Grappendorf integrator and amplifier/inverter

Something confusing me for a little while was that, in the Grappendorf components provided, there is no inverter module. But after looking at some of the project photos, I realized that all I needed to do is add a resistor to the amplifier module.

=> Grappendorf amplifier module schematic

That is, you just add a 100k resistor from IN- terminal to the amplifier output (AMP) terminal. Your input signal is attached to 1x1 or 1x2. Then, your feedback resistor matches your input resistor and you get -1 gain. Here is the signal from the inverter fed with a sine wave:

=> inverter I/O — yellow input, green output

I set up the integrator and inverter to solve simple equation ẏ = y, and this appeared to be working, at a glance:

=> integrator and inverter signal output

If I start with initial condition 0V or lower, I get the negative curve, but if the initial condition is a positive voltage, the curve goes up. I suppose that represents either -exp(x) or exp(x).

Copyright

This work © 2025 by Christopher Howard is licensed under Attribution-ShareAlike 4.0 International.

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