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OP- Amp Circuit
4

OP- Amp Circuit

OP- Amp Circuit

(OP)
Can anyone explain this circuit to me?

Why is the  feedback resistor at the non-inverting input?

RE: OP- Amp Circuit

The opamp is being used as a schmit trigger.   

RE: OP- Amp Circuit

You are probably familiar with negative feedback.  This circuit has positive feedback. Positive feedback prevents the switching from jittering on slow changing signals.

RE: OP- Amp Circuit

Looks to me that the hysteresis is backwards from normal though.  The threshold appears to be closer to the input signal state rather than farther.  The feedback resistor value is not specified, so...

The fact that the OP is calling a comparator an op amp is likewise mysterious.  Did you read the datasheet?  See page 8 of http://www.datasheetcatalog.org/datasheet/nationalsemiconductor/DS005706.PDF  This circuit appears to be a mixture of two hysteresis reference circuits at the bottom of the page.

TTFN
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RE: OP- Amp Circuit

(OP)
The datasheet was helpful.  It appears to have the official name Non-Inverting Comparator with Hysteresis.

Thanx All.

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