OPA376: Capacitive drive simulation

Daniel Sigtryggsson

Part Number: OPA376
Other Parts Discussed in Thread: OPA364

Tool/software:

I am using OPA376 as an ADC reference buffer (unity-gain). I have 5 instances of ADCs and we have found that we need to DM filter the output of the OPA376

That being said I understand from the datasheet that the OPA376 can drive 250pF in unity-gain configuration. Now we have 4.7k resistor on the output of the buffer that serves as an isolation resistor and the R element in our RC.

How can I ensure that we have a stable OPA376 with these 5 RC filters ?

Below you can find my simulation schematic, how do I go about extracting the simulation

11 months ago

0 Ron Michallick 11 months ago

TI__Guru**** 165346 points

Daniel,

OPA364 or OPA376?

Regardless of the load, I combined all 5* because they match, this break works for unity gain setup.

*This is not required. They can remain as 5 separate loads.

0 Daniel Sigtryggsson 11 months ago in reply to Ron Michallick

Prodigy 40 points

Hi Ron,

It is OPA376. My simulation model was wrong. why do you add L1 ? And is my circuit below essentially the same to determine my stability margin ?

+1 Ron Michallick 11 months ago in reply to Daniel Sigtryggsson

TI__Guru**** 165346 points

Daniel,

You measured forward single gain. The lack of gain peaking suggest good phase margin, but you can't read phase margin this way. Stability depends on the feedback loop. You have to break the loop to measure the loop. Lastly, the IN+ pin has no DC solution, so it may not work in reality.

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OPA376: Capacitive drive simulation