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Why we don't use positive feedback

Positive feedback usually does more harm than good as it drives the system in which it is used into saturation at one limit or the other. Now that I've panned it there was one scheme I know of which made use of it in the distant past. This was the "super regenerative" radio receiver used in the very early days of radio in which a transformer with a movable coil was used to inject a bit of the amplified signal into the input. It worked after a fashion but it would break into oscillation at the least excuse. It is only of historical interest now.

In addition to Mr. Foxx' comment, here an extract from Texas Instruments' application note: SBOA093A (which you can download from their main site), page 14: (bold formatting is added by me)

Consider the open loop amplifier used in the circuit of figure 10. Note that no current flows from the source into the inverting input - the summing point restraint derived in the previous section - hence, there is no voltage drop across RS and ES appears across the amplifier input. When ES is zero, the output is zero. If ES takes on any non-zero value, the output voltage increases to saturation, and the amplifier acts as a switch.

The open loop amplifier is not practical - once an op amp is pushed to saturation, its behavior is unpredictable. Recovery time from saturation is not specified for op amps (except voltage limiting types). It may not recover at all; the output may latch up. The output structure of some op amps, particularly rail-to-rail models, may draw a lot of current as the output stage attempts to drive to one or the other rail. For more details on op amps in open loop operation, consult reference 1.

The reference 1 is another of their application note: SBOA092B.

So, unless you want a switch which may latch, or not, ...

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It seems that there is some confusion.

It is not about consumers feedback.

"In electronics, feedback is defined as the process of returning part of the signal output from a circuit or device back to the input of that circuit or device."

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