OPA2990: The S/H circuit application

David Huang

Part Number: OPA2990

Hi Team

My customer is try to make a S/H circuit using the OPA2990, and they want to know whether the open-loop or the close-loop is better for this application considering the accuracy.

Also, is the follower output or the integrator output better if the close-loop setup is used?

Please let me know if we have any application notes regarding this as well.

Regards

David

over 2 years ago

0 Caro Walter over 2 years ago

TI__Genius 17447 points

Hey David,

By S/H circuit do you mean sample and hold? If so, could you tell us which ADC the customer is using? I imagine the ADC has relevant app notes that we might leverage.

All the best,
Carolina

0 David Huang over 2 years ago in reply to Caro Walter

TI__Intellectual 2285 points

Hi Carolina

Thanks for your response!

The customer is using the AD port of TM4C1294 for the ADC.

Regards

0 Caro Walter over 2 years ago in reply to David Huang

TI__Genius 17447 points

Hey David,

I found this powerful application note that uses the LF398 but the theory may be applied to OPA2990: https://www.ti.com/lit/an/snoa223/snoa223.pdf

As for the customers actual question: "For applications requiring high accuracy, one can use the closed loop-architecture, with either a follower output (Figure 8) or an integrator output (Figure 9). The feedback significantly improves the accuracy of the S/H relative to the open-loop configuration, although the speed is somewhat less."

I recommend sharing the app note with the customer.

All the best,
Carolina

0 David Huang over 2 years ago in reply to Caro Walter

TI__Intellectual 2285 points

Hi Carolina

Thanks for answering!

The customer add an additional question after checking the collateral, could you provide an answer to the question below as well?

'The application note is about the LF398, but is the OPA2990 also good for close loop applications? Also, for close loop application, if pulling the SHUTDOWN pin of the first op-amp to high, will the output be cut off as expected, or will there be any other response?'

Regards

David