compensating opamps???!?!?

[Brian Marshall]

Ok,  I've been looking at a few schematics, and have run in to a few that have 'compensating' opamps.  Usually single opamps in an 8 pin package with one unused pin.  They all seem to allow you to bias within the opamp, but also have a compensating pin.  What the hell does that do?

[Nasse]

Propably better info and more could be find somewhere but I remeber that some opamps are not stabile at all gains, one thing to look at data sheets and often seen statement is "unity gain stable". If you set the gain too low for such opamp that is not capable of it, it may oscillate or freq response or other performance is poor. Some opamps are "internally" compensated so you dont normally need any compensation, but it means that some compromises may have been done. Why some opamps have external pins so you can tailor compensation just what is needed and nothing more is because that way yuo can have better performance, and you are then talking about higher slew rate and better bandwith.

Sorry my english and knowledge. Maybe compensating can be used for some desired "lo-fi" effect or distortion. But guess there may be some risk of increased transient intermodulation distortion, and that sounds awful. Two Finnish scientists discovered transient intermodulation distortion. The other was tube amp fanatic and guru. He simply was thinking why was it so that the better the distortion specs of a transistor or tube amp were, the more it sounded like shit. But that is another story :wink: