You're still limited by the precision of the base capacitor C. But I guess there's more choice of high-precision capacitors at lower capacitances. You can buy 100 nF +/- 1%... 100 uF, probably not so much.
Hmm, okay, but a variable resistor gets you a variable capacitor? But not the energy storage so you can't really tune a tank circuit with that to make a tuner. I'm sad that the old variable capacitors with plates are now like $50 each qty 1.
Yeah. At high frequencies, you also run into op-amp speed limitations, so it gets dicey (although there are some pretty fast unity-stable op-amps out there).
But ultimately, it's one of these areas where the answer is increasingly "why don't you just synthesize this with a programmable chip".
I was thinking on using this to mimic a varicap diode.
So can you use this circuit to make and arbitrarily precise capacitor?
You're still limited by the precision of the base capacitor C. But I guess there's more choice of high-precision capacitors at lower capacitances. You can buy 100 nF +/- 1%... 100 uF, probably not so much.
Hmm, okay, but a variable resistor gets you a variable capacitor? But not the energy storage so you can't really tune a tank circuit with that to make a tuner. I'm sad that the old variable capacitors with plates are now like $50 each qty 1.
Yeah. At high frequencies, you also run into op-amp speed limitations, so it gets dicey (although there are some pretty fast unity-stable op-amps out there).
But ultimately, it's one of these areas where the answer is increasingly "why don't you just synthesize this with a programmable chip".