BGR with OPamp looks like closed loop system,
as shown in attachment "BGR_sch.jpg".
I was also wondering about its noise performance,
and posted relevant topic.
Some answer was :
Break the loop, insert noise source, and do .noise simulation
if your bandgap include OPA,you must insert noise source in the loop of the bandgap system;but your bandgap only used transistors , you may refer to analysis of noise in transistor at chp.7 of design of analog CMOS integrated circuits by Razavi.
If case of schematic attached by me, voltage between v- and v+ could be different by <40mV for comercial temperature range, and
YES the opamp gain (20+dB) does looks too low to me.
Silicon results is 1.17V+/- 40mV for 50 samples, and temperture curvature to be measured.
I'll keep you posted for furthur temperature results.
The simple way to get the noise volt in rms: put a ac source at the vcc, and do noise analysis, get output voltage noise spectral density, and take the rms value (from low freq to 100kHz should be enough). This way you can simply get the output noise in rms (in certain bandwidth).
orley said:
if your bandgap include OPA,you must insert noise source in the loop of the bandgap system;but your bandgap only used transistors , you may refer to analysis of noise in transistor at chp.7 of design of analog CMOS integrated circuits by Razavi.