OPA1642: Less than unity gain?

Jerry Gorman

Part Number: OPA1642

Any chance the OPA1642 in inverting mode is stable at 1/3 gain? R1 is 10K feeding the negative input and R2 the feedback resistor is 3.33K. Needed over audio range. This seems like a no-no but I have to ask as I'm dealing with a board that is already laid out. Just looking for an opinion.

over 3 years ago

0 Raymond Zhang1 over 3 years ago

TI__Mastermind 47796 points

Hi Jerry,

Q: Any chance the OPA1642 in inverting mode is stable at 1/3 gain?

The op amp configuration with gain of 1/3 described above does not have adequate phase margin (29.14 degree) at its unity gain BW.

In order to make the circuit stable, 22pF capacitor is added in parallel with R2, 3.3kOhm. The phase margin is 70.9 degree and the simulation is shown that is stable.

If you have additional question, please let us know.

/cfs-file/__key/communityserver-discussions-components-files/6/OPA1641-E2E-BW-0.33Gain-11092020.TSC

Best,

Raymond

0 Jerry Gorman over 3 years ago in reply to Raymond Zhang1

TI__Prodigy 300 points

Thank you Raymond

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OPA1642: Less than unity gain?