LMxxxx chip as a buffer inside feedback loop?

[300_baud]

hi guys,

i just wanted to know if anyone has used the lmxxxx series of chips inside a feedback loop as a buffer with a opa627 (or slower chip) as the main opamp?

Is this even possible or is the lmxxxx not stable as a buffer?

Thanks,
300_baud

[Sheldon]

Originally posted by 300_baud
hi guys,

i just wanted to know if anyone has used the lmxxxx series of chips inside a feedback loop as a buffer with a opa627 (or slower chip) as the main opamp?

Is this even possible or is the lmxxxx not stable as a buffer?

Thanks,
300_baud

Unstable at gain less than 10.

Sheldon

[SheldonD]

Small correction here: opa627 is unity gain stable but 637 needs gain =/> 5 according to the data sheet.

[carlosfm]

Originally posted by 300_baud
i just wanted to know if anyone has used the lmxxxx series of chips inside a feedback loop as a buffer with a opa627 (or slower chip) as the main opamp?

OPA541/8/9 chips are stable at gains of 1.
But to include anything inside the feedback look of a signal op-amp it should be as fast or faster.
Power op-amps are (much) slower than most signal op-amps.