Op Amp Offset Null

[bkanber]

Heyo... I'm not used to working with single op-amps.. the single op amps have two offset null pins. I sort of understand what these are used for, but my question is: will the op amp still work as expected if I don't connect the two offset pins (1 and 5) to anything?

Thanks,
Burak

[aron]

Should be fine if the schematic doesn't call for using them.

[JDoyle]

Yes.

And if you are doing things like we normally do here and coupling stages together with caps, offset voltage doesn't even really matter 99% of the time.

There are situations where it makes a difference and can effect things, but they are subtle. For example, in the TS circuit, an offset voltage will cause one polarity of the waveform to be more heavily clipped than the other as the offset forces the output signal to drive the corresponding diode further into it's conduction curve.

But whether you use the null pins to zero out the offset or not, it would still be a TS (though you would of course now need another single op amp for the tone section).

Personally, I think that any pins you find available should first be thought of as options to mess with the internal circuitry, secondly as for what they were intend. Rarely do we need to use EITHER the offset pins or the frequency compensation pins when they are provided, but they DO provide some great opportunities to abuse the hell out of a chip...

But in answer to your question, as long as you have the input, output and power connections properly connected, everything will work as it should.

Regards,

Jay Doyle

[aron]

Jay,

What effect does altering the offset do vs, altering the bias resistors for VREF? Is it similar?

[Eb7+9]

usually refers to the offset that is created by the mismatch in the front-end devices in the op-amp or some other mechanism and is intended for use in DC-coupled circuits where a (close-to) zero volt average output is required ... in AC coupled circuits this won't matter much as long as the offsets are low enough ...

in a single-rail circuit if you had offset problems that couldn't be fixed this way then you might adjust Vref to set the output right between Vcc and ground or wherever you wanted it ...