[time-nuts] high rev isolation amps

Bruce Griffiths bruce.griffiths at xtra.co.nz
Tue Mar 29 21:51:20 EDT 2016


With most of these old circuits reducing the LF noise contribution to the emitter/collector current by the biasing circuit by utilising lower noise power supplies and/or using improved biasing methods can improve the clse in PN significantly.
The PZT3904 and PZT3906 are still available.
Bruce
 

    On Wednesday, 30 March 2016 1:00 PM, Bob Camp <kb8tq at n1k.org> wrote:
 

 Hi

There were (and maybe still are) SOT-89 versions of the 2N3804 and 3906. They will handle more
power than most of the other versions. That gives you better Vce on the string. They also have less
package inductance which helps tie the base to ground. If you are building some of those circuits, they
are worth looking for.

Bob

> On Mar 29, 2016, at 6:47 AM, Charles Steinmetz <csteinmetz at yandex.com> wrote:
> 
> See below for schematics of the NIST isolation amplifiers from 1990 and 1997.  NIST reported the isolation as >120dB.
> 
> I built isolation amplifiers similar to these (with lower-noise power supplies and biasing tinkered slightly for better dynamic range), and with careful construction achieved isolation substantially better than 120dB (see my post of 11/25/14 for more details).
> 
> Best regards,
> 
> Charles
> <NIST_120dB_isolation_amplifier_schematic_email.gif><Iso_amp_NIST_schematic_with_values_5MHz_1997_email.gif>_______________________________________________
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