[volt-nuts] 731A output impedance
WB6BNQ
wb6bnq at cox.net
Tue Nov 27 22:33:16 UTC 2012
Hi Ed,
I am a little confused with regard to your paragraphs 3 & 4. Could you elaborate
on those two paragraphs ?
thank you,
Bill....WB6BNQ
ed breya wrote:
> The simplest way to drop the output impedance without adding much
> circuitry is to just change the series R to 100 ohms or so - that
> would still give pretty good isolation from capacitive loading.
>
> If the R is dropped to zero, the DC performance will be best, but
> you'll have to worry about the amount of capacitive loading. If the
> lines are short - say a couple of meters or less of open wire, it
> would probably be OK, but that much coaxial cable may make it oscillate.
>
> The suggestion to get the feedback right from the output terminal,or
> even with external sensing at the load would be best for DC accuracy,
> but would have the same problems as above.
>
> You can also take the DC feedback from the output directly, and the
> AC feedback from the amplifier output, while the series resistor
> isolates the two. This would give good DC accuracy and AC stability,
> but would alter the dynamic response and LF noise shape somewhat.
>
> If you add an amplifier, you'll of course have to consider its offset
> and noise contribution, and it will have the same stability issues to resolve.
>
> Ed
>
> _______________________________________________
> volt-nuts mailing list -- volt-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
> and follow the instructions there.
More information about the volt-nuts
mailing list