modified 7 years ago

Op Amp Buffer

00:50:40

Used for stepping down analog voltage from 14V to the range used by an 3.3V ADC. Ive modeled two ADC's here for demo purposes (10k Resistor and 14pF cap), but based on the results I'm not seeing why I need the Op Amp. Heard people mention higher impedance on voltage dividers, but this doesn't drain a lot of current and both produce about the same result.

published 7 years ago

592azy2circuitdude

7 years ago

I think it is as you said... the opamp is just used as a buffer. The opamp is wired as a voltage follower, which means the input voltage is just passed to the output. It's used to help isolate the voltage divider from the ADC. Here it doesn't really matter because the ADC doesn't effect the voltage divider much. I hope that helps.

cannellajs2

7 years ago

@592azy2circuitdude Thanks for your insight, I think my previous circuit wasn't insightful was because I was using the same voltage divider to test the response. I've updated it so you can clearly see how the added load of the ADC effects the results of the voltage divider without a buffer Op Amp. I added the Resistor and external capacitance at the suggestion of this article https://www.embeddedrelated.com/showarticle/110.php to help the ADC remain stable when the ADC is actually sampled.

592azy2circuitdude

7 years ago

I'm glad. Thanks.

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