Miniaturization

I have no idea. What else would you give besides the 5mA ?>:-} ...Jim Thompson

Adulation.

Cheers

Phil Hobbs

Sno-o-o-o-ort ;-)

What kind of noise level are you trying to achieve? ...Jim Thompson

Well, better than -160 dBc/Hz, ideally. So maybe 10 nV in 1 Hz for a

Cheers

Phil Hobbs

Ouch, As you know a cap multiplier will give that sort of noise level. For an IC, it would have to be an external cap.

George H.

LM329s are about at that level, for super cheap. Cap multipliers can be 20 dB better than that, but of course not near DC.

Cheers

Phil Hobbs

Should be about 1mA required, provided you are not interested in the noise in the region where the transistors have 1/f noise.

Try it in LTSpice - though I couldn't see an easy way to multiply the size of a transistor and ended up using copy/paste.

But that's where it's super hard to filter!

Nulling measurements are one good solution in that case--about 5 years ago, I did a compact actively-stabilized laser that had an Allen variance below 1E-10 at 10,000 seconds. You can't do that single-ended on account of the instability of the laser amplitude and the available voltage references.

Cheers

Phil Hobbs

True, 1/f noise would not be easily fixed with filters. Similarly, if you start with some reference that is horribly noisy at all frequencies, and filter it with big capacitors to get decent noise at say 10kHz, that may also be unsuitable where low frequency noise is your main concern.

Because of my application (powering a VCO, inside a PLL) I did not care about noise at very low frequencies. Perhaps it was good, I didn't pay attention.

Incidentally, I find the 1/f noise "corner frequency" to be very misleading to many people. They love to choose the device with the lowest "1/f corner". Those people are easily pleased, by adding more white noise to an otherwise quiet circuit, which then makes the "1/f corner" occur at a lower frequency. I have been tempted to do it. A better metric is required for marketing these things in an honest way.

Chris

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