[time-nuts] Replacement A9 boards for the HP 5065A
ewkehren at AOL.com
Mon Feb 26 10:20:43 EST 2018
We have decided to go with the 1012 do we need to do any thing with pin 5Bert kehren
Sent from my Galaxy Tab® A
-------- Original message --------From: Attila Kinali <attila at kinali.ch> Date: 2/26/18 9:53 AM (GMT-05:00) To: Discussion of precise time and frequency measurement <time-nuts at febo.com> Subject: Re: [time-nuts] Replacement A9 boards for the HP 5065A
On Sat, 24 Feb 2018 23:44:16 -0500
Charles Steinmetz <csteinmetz at yandex.com> wrote:
> Given the relatively low resistances at the op-amp inputs (10k ohms),
> the ultra-low input "bias" (leakage) current of the 6240 is simply
> unnecessary. Any offset due to the input currents (within the general
> range of any of these op-amps) is insignificant compared to the op-amp's
> offset voltage. Thus, offset voltage, offset voltage tempco, and offset
> voltage long-tem drift are the critical parameters (as Poul-Henning
> pointed out). And here, the 1012 is clearly the best of the three. In
> addition to having the lowest input offset spec, the 1012 has guaranteed
> maximum specifications for these important parameters. The 6240 (for
> good reason) is *not even rated* for long-term stability (drift).
> (Long-term offset stability is a particular weakness of CMOS op-amps.)
Oh.. right, I didn't think about long term behaviour. Thanks for the correction!
BTW: How about using an LTC2057 then? Its input bias current and
GBW spec is similar to the LT1012, but its offset voltage and drift
are far superior. Or would its charge injection noise be too large
for this application?
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