Thanks Michael, for your very detailed answer. But few things are not clear to me. Can you please explain?
1. Why do we need to bias a BJT at high β? Since in a CMOS bandgap emitter current and not the collcetor current
is used to obtain ΔVBE, I think, β value should not matter.
However I think, low β coupled with high RB might cause some problem as vb of two BJTs
will not be at zero and MAY not be EQUAL. Am I right?
2. I have checked RB, RE, and RC values for 2X2um, 5x5um and 10X10um BJTs of 0.15um TSMC technology.
To my suprise I found that RB and RC values are almost same for all, though RE decreases as the size increases.
I think, thus one is not getting any benifit by going to high area from Rb perspective alone.
3. I am eager to know the method to compensate Rb effect. Can you please
post it?