AW: Re: AW: RE: ASM-1 and other question

[Haible_Juergen#Tel2743]

> One solution is to split the resistor in 2 resistors in series
> and put a capacitor between ground and the node where the two
> resistors meet. This works if the resistor is supposed to be
> between constant voltages (e.g. between Vcc and the virtual ground
> at the inverting input of an opamp).

Yes, that's what I did on my SEM-VCO clone. (There was a resistor
divider for the reference current anyway, so I just had to add the
capacitor).
I am not sure if it was actually necessary *there*. I think both the
uA723 in the SEM design and the RC4195 which I used are
remarkably better noise-wise than the 78xx stuff. But I'd have
to look this up - not sure now, from memory.

General question about voltage regulator noise: Why *are* they
so noisy? I understand that zener diodes are quite noisy, but
most regulators use other means to get their reference voltage,
don't they? band gap?

JH.