On 24/12/2016 04:34, "Glen Slick" <glen.sl...@gmail.com> wrote:
> On Fri, Dec 23, 2016 at 7:48 PM, Brent Hilpert <hilp...@cs.ubc.ca> wrote: >> >> The op amp is configured as a schmitt trigger or comparator with hysteresis: >> There is no negative feedback so it is operating at full gain and >> functions like a comparator. >> However there is positive feedback via R412 (*1), this adds >> hysteresis to the trip point(s). >> (Brief hackneyed, not rigorous, theory of op: As the input >> differential varies past the trip point, the output pulls the + input >> further above or below the point at which it just tripped, so the >> inputs now have to 'overcome' a greater differential >> to trip as the input differential varies in the opposite direction.) >> > > A recent EEVblog video has some whiteboard explanation of using > positive feedback for hysteresis if anyone is curious... > > EEVblog #941 - Schmitt Trigger Tutorial > https://youtu.be/Ht48vv0rQYk?t=13m43s Ah cool, I was watching some of Dave's tutorials yesterday but in one of them he lost me completely towards the end, talking about Virtual Ground on op-amps. Cheers, -- Adrian/Witchy Binary Dinosaurs creator/curator Www.binarydinosaurs.co.uk - the UK's biggest private home computer collection?
