High precise DC amplifier for multimeter?

[Valjean]

Could someone estimate the parameters of the input amplifier of the Agilent 34401A be compared with AD8610 ?
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[crutschow]

What is this for? Are you trying to build a DC amplifier for a standard multimeter?

 

[Valjean]

DC amplifier for 6,5 digit multimeter
Look around how difficult it would be to suggest something like 34401A
The amplifier considerations in
Reinforced 1x, 2x, 10x, 100,
max output voltage of + -3.2 V,
low noise, max linearity,
input resistance in order GOhm.

 

[FvM]

I believe that AD8610 can achieve similar performance. But I'm unable to derive DC linearity from the datasheet. It should be verified by measurements.

Possibly additional loop gain is necessary to achieve sufficient linearity in x100 gain configuration.

Please consider that the DC offset specification of 34401A requires an external autozero.

 

[carpenter]

I think 34401A measures the alternately, input voltage (measure customer input (MC)) and them measuring the voltage path to ground (measure zero input (MZ))
The final measurement result is computed from MC–MZ.

 

[crutschow]

For minimum DC offset you could use an autozero op amp circuit such as this. It has a typical open-loop gain of 140dB so will have negligible gain error at a closed-loop gain of 100.