Experimenting with Op Amps: Schmitt-trigger

RE: Experimenting with Op Amps: Schmitt-trigger

phoenixcomm — Sat, 20 May 2023 20:09:33 GMT

[mention:acaf6a9338de4eef8f6717d5561ed01d:e9ed411860ed4f2ba0265705b8793d05] Jan, why in the world do you want to go down this rabbit hole? I still don't understand why. If you need a Schmitt Trigger then use a Schmitt Trigger. LOL I do like your bench.

RE: Experimenting with Op Amps: Schmitt-trigger

DAB — Sat, 20 May 2023 18:16:31 GMT

Well done Jan.

I remember when the first schmitt trigger IC's came out.

They were so useful for debouncing switches and buttons.

RE: Experimenting with Op Amps: Schmitt-trigger

Jan Cumps — Fri, 19 May 2023 12:29:19 GMT

If you wonder why the input levels aren't 1/3 and 2/3 of Vref in my example (as [mention:4f57fc9d538949ad9eb336ddb9469bb8:e9ed411860ed4f2ba0265705b8793d05] explains, but I [mention:abc02a6f3bb4446b8ba40c3d1b87fd8c:46448885d0e64133bbfbf0cd7b0fd6f7] ): my op-amp does not swing to the positive rail. With Vref = V+ = +5 V, the output swings to 3.5 V.

Once Jon's post returns, you 'll see the hints.

RE: Experimenting with Op Amps: Schmitt-trigger

scottiebabe — Fri, 19 May 2023 12:10:35 GMT

Very cool JC! Was the ARB wave defined by you or was it built-in to the AWG?

RE: Experimenting with Op Amps: Schmitt-trigger

jc2048 — Fri, 19 May 2023 11:51:12 GMT

I'm not totally convinced by all of your explanation.

I think I'd do it by first substituting the Thevenin equivalent of R5 and R6, like this

That then makes it more obvious how the switching level derives from what the output is doing (in this case, a third of the difference of the output from 2.5V).

Does necessitate an understanding of Thevenin, but that's useful to have anyway if you're going to do analogue design.

RE: Experimenting with Op Amps: Schmitt-trigger

genebren — Thu, 18 May 2023 20:23:36 GMT

Great experiment! It is very informative to try out circuits in this way, as it allows you to try various combinations of component to achieve the desired results. Interesting and well done!