OPA188: Input bias current

Gerhard Kreuzer

Part Number: OPA188
Other Parts Discussed in Thread: INA149, OPA2188, OPA2192

Hi,

I have to accurately measure a differential voltage of +-80V or +-8V or +-2V upon +-400V common mode voltage. The OPA188 offers really good noise and offset parameters, ideal to measure DC, but with a bias current of 1.5nV this will induce a high error voltage at the resistors I need. Any idea how to solve this problem?

Input is differential, output is differential (so I Need 2 OPA188, no problem), Input Impedanz should be >400M Output volatge should be +-4V F.S. for all three ranges. Supply is +-15V.

With best regards

Gerhard

over 8 years ago

0 Marek Lis over 8 years ago

TI__Guru 69591 points

Gerhard,

If the input bias current is a major concern, instead of OPA2188 please consider using OPA2192 with maximum IB and Vos at 25C of +/-20pA and +/-25uV, respectively. But I believe the best approach might be to consider using INA149 with the input common-mode and differential voltage up to +/-275 and +/-13.5V, respectively.

0 Gerhard Kreuzer over 8 years ago in reply to Marek Lis

Expert 2630 points

Sorry, but I Need a fully differential Output.

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OPA188: Input bias current