[quote author="jhaible"][quote author="bcarso"]And the damn thing is floating too![/quote]
Yes. You could connect the capacitor to GND instead - that would give lowpass filtering of PSU ripple (mostly) independent of the load. Or, they way it is drawn here, capacitor connected to the emitter / source side,
emulates an inductor, i.e. the filtering is done by the interaction of the gyrator circuit and the load.
I don't know which method is better in an absolute sense, but that gyrator is great when you want to emulate a huge piece of iron in a traditional power supply without changing the general behaviour of the original.
I don't think this is any good for signal processing, though.
JH.[/quote]
But---yes not any good in its present form for signal processing but if "suitably" refined...might be fun as they say.
In an old automotive amp at H*rman, Brad Plunkett did something a bit similar and it came to be called colloquially the Plunkductor, but I don't think he ever analyzed it in terms of being a gyrator of sorts. It "got out of the way" when there was some moderate signal present and became more or less a short circuit.