THS4631 bias current

Hello Keichi,

  I will ask some  of the engineers and see if we have any evaluation data. In the meantime would the other products that Randy mentioned be a suitable alternative?

Samir.

Hello Keiichi,

 I asked around and it doesnt look like we have any formal test data on the behavior. The behavior was only simulated to find and understand the root cause.

Samir

Samir,

Thanks for your reply.

The customer using this Opamp for LCR meter, so Ib will be a important factor.

Can we share simulation data for reference? I know this is a just reference, not for guranttee, but it may help

customer to understand device behavior.

I also ask customer to replace OPA659, OPA657 or OPA656. But it seems offset will be large against THS4631.

Hello Keiichi,

 I spoke to one of the designers who had investigated this issue years ago. He mentioned that he had run the simulations for understanding but never saved the data. Unfortunately this is on a very old, obsolete process so we dont have the ability to go in and resimulate as the tools have since changed. I am really sorry about this.

By the way is the customer Chroma by any chance?

Samir

Samir,

Thank you for your reply.

I understand your situation. The THS4601 which you suggested for alternative is rejected due to high price.

And +- 12V is mandatory, therefore others can not use.

Our customer is now in ES phase, already fixed their board's artwork, so p2p alternative is required.

Hello Keiichi,

  Given that it is in an LCR meter application, does it need very high bandwidth? Will the OPA627 or OPA827 be suitable alternatives?

Samir

Hello Samir,

The GBW should be greater than at least 70MHz, so OPA627 and OP827 would not be alternative.

The competitor's chip shows same phenomena, but shows dependency is small against THS6431.