[time-nuts] V refs -- Bruce

[Richard Moore]

On Nov 30, 2008, at 3:39 PM, tBruce wrote:

> Message: 6
> Date: Mon, 01 Dec 2008 11:53:32 +1300
> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> Subject: Re: [time-nuts] V refs
>
> The uA714 is claimed to be an OP07 equivalent.
> A chopper stabilised amplifier would have lower drift and flicker  
> noise,
> however the zener drift and flicker noise probably dominates.
>
> Stacking LTZ1000's in the same way is a little tricky.
> The only satisfactory method I have devised so far uses a PJFET as a
> voltage controlled resistor to sink the zener current whilst  
> allowing it
> to be reused to bias lower LTZ1000s in the series stack.
>
> Bruce

Bruce, The 714 opamp provides gain in the Datron 1082, and I would  
use one LTZ1000 (or two in parallel, rather than try to use them in  
series). A while back I tried using two LM399s in series in a Fluke  
895, and really didn't like the results -- a single 399 with an amp  
was better in every way I could measure. As an alternative to a  
chopper like the 1151, I might consider an OPA27. I have used the now  
unobtainable OPA111 in the past, and that was a superb DC amp; they  
(TI) claim the OPA27 is as good.

Dick Moore