Inverting or non-inverting amplifier with positive feedback

Positive Feedback

Hi

Is the circuit an inverting or non-inverting amplifier with pos.feedback

I think it an inverting one but I read in a paper that it is an non inverting pos.feedback amplifier.

Who's wright???

Greetz E-goe

It is inverting with positive feedback but you can hardly say it is an amplifier if it is made with op amp. All depends on open loop gain of amp and value of resistors.

It is not an amplifier, rather this is a latch or a Shmidt trigger. Think of it in the following way - you have Ve<Vin<Vc. Then you switch the power on. If we assume that initially the output of the opamp is @ 0v then the (+) input is at 0 as well. If Vin>0 the opamp output starts going down to Ve and the (+) input also follows through the divider which further drives the output down to Ve - so, positive feedback and the opamp saturates at Ve. The (+) inout gets a voltage that is defined by the divider between Ve and gnd. The same thing happens but in the oposite direction if initially Vin was <0. Now, if you start changing Vin, the opamp output will flip when Vin crosses the voltage at the middle tap of the divider. The values of the resistors are important only for setting this trigger points - they are two.

It is a trigger. (an inverting one)

It can be found in any book about IC design (for example: Gray)