Why does the regenerative circuit not saturate?

I answered this SE EE question yesterday.

The positive feedback in a Schmitt trigger is "self-reinforcing" ie, the output voltage rises uncontrollably like a snowball in an avalanche. Here, this effect is useful since it accelerates the transition and, in this way, it converts an analog circuit into digital one.

In amplifier circuits like Armstrong's regenerative circuit, the positive feedback is "dosed" so that there is no continuous increase in the output voltage, only some additional amplification. It is hard to imagine how this amplification happens, especially when we make a follower amplify (I suppose there is some effect of accumulation), but it is a fact.

It is interesting to compare the two types feedback circuits:

• In positive feedback circuits, from a low-gain amplifier we get a high-gain amplifier.
• In negative feedback circuits, from a high-gain amplifier we get a low-gain amplifier.

Historically, in the past they used positive feedback to make amplifiers because they did not have high gain amplifiers. Now we have amplifiers with excessive gain and we low it to get stable amplifiers with fixed gain.

In today's positive feedback circuits like Wien oscillator, the Armstrong's knob is implemented by a non-linear element.