# Need help understanding amplifying voltages **URL:** \ **Category:** DIY STUFF\ **Created:** [February 2, 2022, 9:32pm UTC](https://lookmumnocomputer.discourse.group/t/need-help-understanding-amplifying-voltages/4587 "2022-02-02T21:32:49Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![hitachii](https://avatars.discourse-cdn.com/v4/letter/h/b5ac83/32.png) [@hitachii](https://lookmumnocomputer.discourse.group/u/hitachii)\ **Post date:** [February 2, 2022, 9:32pm UTC](https://lookmumnocomputer.discourse.group/t/need-help-understanding-amplifying-voltages/4587/1 "2022-02-02T21:32:49Z")
Welcome to Amateur Hour. Currently trying to convert a 3.3v signal from my Axoloti into 5v signal for CV. The 5v is arbitrary and I plan to change it once I know what I’m doing here. This is my first venture into doing a circuit by myself and I figured that the non-inverting amplifier would do the trick. ![Example-non-inverting-Op-Amp-circuit](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/e/4/e4f41cc84b025450d35075bb9274c141b03446d4.png) For R1 I’m using a 1k resistor, and for R2 it’s a 620 ohm. The op amp is connected to my ±12v power supply. For context for the next images, Axoloti is a development board that uses a Max/PD-like patching interface. It has an onboard 8-bit DAC which is 0 - 3.3v. Using a ‘dial’ I can control the DAC as seen in the picture. ![Success](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/d/1/d110bd76446ca2385d121e7aeb752d50e74190e8.png) ![Wut](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/5/5/5582041418d82c662f23caa7b01513bc5ee0ccdd.png) Currently, when the dial is at max, the DAC output is 5.24v, but when I turn the dial down all the way, the voltage goes up to +10v. I want it to go the other direction to 0v! So I’m halfway there, but how do I make the voltage go _down_ instead of _up_ when I reduce the DAC voltage? Thanks! ---
**Author:** ![tamasgal](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/tamasgal/32/16249_2.png) [@tamasgal](https://lookmumnocomputer.discourse.group/u/tamasgal)\ **Post date:** [February 2, 2022, 10:01pm UTC](https://lookmumnocomputer.discourse.group/t/need-help-understanding-amplifying-voltages/4587/2 "2022-02-02T22:01:14Z")
I don’t think you are halfway there, since the +10V makes not much sense. You get 5.24V with an input signal to the non-inverting input of the opamp of 3.3V if it is built like you have shown above (more precisely 3.3V\*(1+620Ω/1000Ω) = 5.25V), so I assume that 3.3V is on the non-inverting input when `dial_2` is at max. If you get 10V at the output with `dial_2` at min, this means that the input voltage must be 6.17V (via 10V/(1+620Ω/1000Ω) = 6.17V). This however makes no sense since you said that the Axoloti development board has an 8-bit DAC which outputs from 0V to 3.3V. My guess is that the circuit is wrong or the software does not what it promises 😉 Do you have some pictures of your setup? Most importantly: have you measured the voltage at the output of the DAC respectively at the non-inverting input of the opamp? Do you see 0V and 3.3V when you set `dial_2` to min and max? Generally it’s always good to start from the input side and follow the signal path. Check all the components (correct values), measure them if in doubt etc. ---
**Author:** ![hitachii](https://avatars.discourse-cdn.com/v4/letter/h/b5ac83/32.png) [@hitachii](https://lookmumnocomputer.discourse.group/u/hitachii)\ **Post date:** [February 2, 2022, 10:14pm UTC](https://lookmumnocomputer.discourse.group/t/need-help-understanding-amplifying-voltages/4587/3 "2022-02-02T22:14:45Z")
Thank you for your very detailed answer. You are correct, the op amp was connected to ground instead of negative voltage. 😅 One of those situations where I’m so dazed from trial and error that the simple things fall out of focus. This is awesome, full speed ahead! ---
**Author:** ![tamasgal](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/tamasgal/32/16249_2.png) [@tamasgal](https://lookmumnocomputer.discourse.group/u/tamasgal)\ **Post date:** [February 2, 2022, 11:03pm UTC](https://lookmumnocomputer.discourse.group/t/need-help-understanding-amplifying-voltages/4587/4 "2022-02-02T23:03:48Z")
That’s how we learn, by making (tons of) mistakes. Enjoy your adventure and feel free to ask for feedback whenever you’re stuck again 🙂