Multiloop offset

[JDAPJ]

Hi!
Sorry, but I have to ask about this:
(This is regarding a pimeta-like setup)

Does the choice in resistor values affect the output offset voltage?

And, if it would be a large offset with the setup, would it be adviceable to just connect a trimpot to the output? (with output on the wiper and +/- voltage on the others)

Hope u have an answer for me...

 

[tangent]

Quote:

Originally Posted by JDAPJ Does the choice in resistor values affect the output offset voltage?

Sure, it can. But input offset errors are not the only cause of output offset. Read this.

Quote:

would it be adviceable to just connect a trimpot to the output?

No. That is not a reasonable way to correct DC offsets.

Better ways are to try to balance the input offset currents, or games with capacitors.

 

[JDAPJ]

Well I'm sorry for giving u a strange question but...

What I was mostly interested in was if the setup with multiloop in a "3" channel amp with virtual ground has this effects. That's why I was referring to the "pimeta".
I too have that info u are referring to but they do not discuss this subject.

About the trimmer, I was thinking about using it in the "ground" channel.
Still not a good solution to use a trimmer..??
Since it's been use before..so why not??

 

[tangent]

Quote:

Originally Posted by JDAPJ What I was mostly interested in was if the setup with multiloop in a "3" channel amp with virtual ground has this effects. That's why I was referring to the "pimeta". I too have that info u are referring to but they do not discuss this subject.

I realize that the article I linked to does not discuss the Jung multiloop specifically. But the principle is the same: you have to adjust the resistors so that the input offset currents do not cause a DC offset. This is more complicated in a Jung multiloop, but it's doable.

Quote:

Still not a good solution to use a trimmer..?? Since it's been use before..so why not??

Yes, trimmers are used for nulling DC offsets, but not on the output of the amplifier! Some single-channel chips have nulling pins, so the trimmer will go between them, or you can put a trimmer in series with the grounded feedback resistor.