Ok, but open loop as I described?
I bicmos design, there are two common "junk" buffers. The junkiest (sp?) is
going up a PNP and down a NPN. No feedback. You live with the vbe mismatch.
Next up the food chain is the long tail pair (diff amp) with emitter follower.
With one gain stage, it is reasonable stable.
-----Original Message-----
From: "John Miles" <jmi...@pop.net>
Sender: time-nuts-boun...@febo.com
Date: Fri, 1 Feb 2013 01:30:24
To: 'Discussion of precise time and frequency measurement'<time-nuts@febo.com>
Reply-To: Discussion of precise time and frequency measurement
<time-nuts@febo.com>
Subject: Re: [time-nuts] Low noise power supplies?
> Are 4 and 5 regulated? Or is the zener picked to compensate for the VBE
> drops?
>
> Any of these circuits where the output transistor is in an emitter
> follower configuration will have its noise effected by the load current,
> since that current directly effects the output transistor
transconductance.
The load in all cases was a couple hundred mA worth of resistance at the
voltage in question, as I recall. It's been a few years since I captured
these plots.
The Zeners were just whatever parts came to hand, 1N474x parts basically. I
didn't care about the 1.4V drop across the Darlington, just the resulting
noise.
-- john
Miles Design LLC
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