OPA857EVM-978: Psudo differential output to single ended

Daniel Zambrano

Part Number: OPA857EVM-978
Other Parts Discussed in Thread: OPA857

Hello,

I bought the OPA857EVM-978, but I won't feed the output to an ADC.

Instead, I will feed it to a passive filter and then to a PID circuit. Thus, I would like to convert the psudo differential output of the OPA857 to a single ended output referenced to GND.

Also, I would like to have the evaluation board DC-coupled. Should I remove the transformer?

Thanks!

over 5 years ago

0 Sean Cashin over 5 years ago

TI__Genius 16426 points

Hi Daniel,

That is fine, since the output is single ended signal, just with a reference, and you can just as soon not use that reference. The transformer is for interfacing with a self biasing fully differential ADC. If you want the signal DC coupled you have to remove it. However, for a PID controller, don't you want to you try to zero out error? The DC output will be 1.825V for zero input.

If DC coupling wasn't necessary you could ground one end of the transformer and have a ground referenced single ended signal.

Best regards,

Sean

0 Daniel Zambrano over 5 years ago in reply to Sean Cashin

Prodigy 20 points

Sean,

Makes sense. Thanks for the reply :)

~Daniel

0 Sean Cashin over 5 years ago in reply to Daniel Zambrano

TI__Genius 16426 points

Could you please indicate whether or not this resolved your issue?

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OPA857EVM-978: Psudo differential output to single ended