OPA1662: unbalanced outputs

Michele Pedroni

Prodigy 110 points

Part Number: OPA1662
Other Parts Discussed in Thread: OPA1652

Tool/software:

Hi,

I designed and built this circuit as a differential ADC input stage.

If I select the x4 gain or x8 gain (changing R3 value) the outputs are completly unbalanced.

If I measure the differential voltage with a multimeter across the two outputs, this is correct.

If I measure the single ended voltage (each output against the ground) the result is unequal, for example with 0.2V input and x8 gain, VF1 is 1.4V and VF2 is -0.2V.

What could be the cause of this behaviour? Maybe this is not the optimal op amp for the application? Something wrong with my circuit ?

thanks

2 months ago

+1 Marek Lis 2 months ago

TI__Guru 63050 points

Michele,

OPA1652 is a high voltage op amp with supply voltage from +/-2.25V to +/-18V. Even though the part will work on +/-2.5V supplies, its linear input common-mode voltage range is limited from -2V to +0.5V while its output range between +/-1.7V - see below. Thus, I believe the issue you see is caused by exceeding one of its linear ranges of operation.

0 Michele Pedroni 2 months ago in reply to Marek Lis

Prodigy 110 points

I get it, thank you very much for your help Marek.

0 Marek Lis 2 months ago in reply to Michele Pedroni

TI__Guru 63050 points

No problem. Good luck with your design.

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OPA1662: unbalanced outputs