[volt-nuts] Matched resistors

[Randy Evans]

Charles,

For the design I am contemplating, the accuracy of the X2 in not important,
only the stability.  For example, if the output of the X2 is 50uV low, I
don't care so long as its always 50 uV low +/- a few ppm over time and
temperature.  The noise could be filtered but its must also be stable.
 Based on what I am hearing, the switched capacitor multiplier doesn't look
promising.

Randy


On Tue, Jul 22, 2014 at 5:40 PM, Charles Steinmetz <csteinmetz at yandex.com>
wrote:

> Randy wrote:
>
>  I agree that there are potentially some serious unknown issues with drift
>> due to time and temperature due to changes in leakage current, charge
>> injection, etc.  I would think some serious characterization would be
>> needed before this approach could be used.
>>
>
> I have used LTC1043s in the voltage-multiplier configuration, and based on
> that experience I believe you will find there are too many surprises hiding
> there to reach your error budget.  First, there are losses in the
> conversion -- IME, even when driving nothing but the non-inverting input of
> an LTC1050 chopper-stabilized opamp used as a follower, the output voltage
> of an LTC1043 doubler is quite a bit (50uV or more) less than [Vin * 2].
>  Second, the output of the 1043 + buffer is about 100x noisier than the
> output of the same reference followed by a non-inverting gain-of-two
> LTC1050 (on the order of 100uVp-p for the 1043 + buffer, about 1uVp-p for
> the non-inverting gain-of-two amplifier in a 10Hz bandwidth, IME).  Also,
> the 1043 noise is not symmetrical, so different DC meters may give readings
> that differ by 50uV from one another.
>
> If you try the LTC1043, I'll be interested to see what you find.
>
> Best regards,
>
> Charles
>
>
>
>
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