P.S. that All Electronics Channel video, why does he have that small (100 ohm) resistor and an unspecified cap in series with it leading to ground from the gate's output? Is that an attempt to bleed away any high frequency noise to ground or something? It isn't shown in other articles discussing uing inverters as amplifiers.
I think that, that video is about a subtly different, area, of this subject area, which perhaps is adding to any possible confusion.
He seems to NOT be using unbuffered parts, i.e. standard HC CMOS versions. Which, seems to have another set of pros and cons.
The advantages, seem to be he is getting (assuming his calculations/measurements are correct, I haven't checked them), a large 1 GHz Gain Bandwidth product. Which sounds rather impressive, for (what can be) an extremely cheap device (until they become increasing obsolete), with 6 in a single package.
Also, a reasonably large gain (NOT compared to a real op-amp), of (he seems to say), 132, after it is reigned in by his circuitry (he seems to say the open-loop gain would be 200, otherwise).
The Capacitor value, is perhaps 100nF (at around 9 minutes, his paper pad seems or diagram, seems to say, 100m, I assume the m doesn't stand for milliFarads, so the 100nF is a guess on my part, as to what they really meant).
He seems to say, that the 100 Ohm resistor and capacitor (100nF), are to reduce the open loop gain, down to 132 (before being further reduced, by the other components). It is specifically controlling the AC loading of the output, hence the resistor, capacitor arrangement.
On the one hand, some op-amp types, can readily come 4 to a cheap package (ignoring component shortages, and price increases, when components are going obsolete). But on the other, it can be fun and very educational, to try things like this.
I assume, that if more than one item was needed. The dangers, of unexpected (difficult to compensate for), component to component (especially the CMOS device(s) in question), variations. Would be risky/worrying for anything beyond, a one-off, (presumed) uncritical hobby/experimental type of project.
Potentially cheap, standard op-amps, have the datasheet characterisation, massive excess open loop gain (so the characteristics, will tend to be as good, or nearly as good, as the gain setting etc, components, surrounding the op-amp) and other features. To help design things, so that things beyond the first/initial prototype, can work well, for years and decades, into the future.
On the other hand, things (before common IC usage), were commonly designed using just transistors. Which have wildly varying Hfe, over things such as current, voltage, temperature and especially device to device changes. So in theory, it can be done.
I wonder if the potentially high currents, hence high package power dissipation and corresponding high die temperature. Could lead to its characteristics, changing too much, over time. Because in pure (1, 0) logic mode, such changes would tend to not matter, until the device reached its end of life. As it just needs to be on or off, the linear aspects, don't matter too much (in pure digital use mode).
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