Dan Clement wrote on Jan 10th, 2012, 6:41pm:I've designed quite a few band gaps and I have yet to see one come out as simulated... With either npn or pnp.
Best thing you can hope for is to build in some metal options or trim.
Besides you will get much more error from the offset and noise of your op amp than I think you will from VCB = 0.
I do agree - which is one of the reasons I suggested going to the old bipolar structures and avoiding the op-amp methods. If its a lateral bipolar with terrible beta, that won't work.
As a general rule a CMOS process BG is using a lateral PNP and
it will need to be trimmed. You can get around
some of the offsets with chopper methods, but the offsets get
gained up so much that generally you got to trim.