I'm trying to learn more about common-mode distortion in BJT opamps. I read in Douglas Self's Small Signal Audio Design, pages 104-108, that common-mode distortion is only a concern with a reasonable high source impedance (several kiloohms). So, if I'm driving an opamp follower from another opamp's output, for example, I don't need to worry.
However, Samuel Groner's paper on opamp distortion seems to imply that CM distortion is a concern even with negligible source impedances–see the test setup for CM distortion on page 8.
Unfortunately, I lack the equipment and/or the ingenuity to do my own tests.
Now I don't know what to believe and who to trust, and my dreams are haunted by shadowy non-linearities. Won't someone hold my hand and reassure me that everything is going to be all right?
However, Samuel Groner's paper on opamp distortion seems to imply that CM distortion is a concern even with negligible source impedances–see the test setup for CM distortion on page 8.
Unfortunately, I lack the equipment and/or the ingenuity to do my own tests.
Now I don't know what to believe and who to trust, and my dreams are haunted by shadowy non-linearities. Won't someone hold my hand and reassure me that everything is going to be all right?