Hi,I will design High PSRR Low power bandgap voltage reference,but i don't know
stability test (AC) circuit whether test schematic is right or not in gif files.
How can design stability test schematic in this bandgap?(ex: look for phase margin? UGB?)
Hi,I upload the clear test schematic,i have does a stability analysis in this bandgap circuit. but, i can't sure whether my inject ac source point is right or not.
If the process has double poly layer, then, Use poly-poly2 capacitor is good. But if not, than the mos tansistor capacitor is better than the poly-metal or metal1-ploy-metal2 capacitor.
Under DC conditions the AC source is shorted to Emitter of Q1. I think, this will affect the operating point of system, even if the DC voltage of AC source is kept as '0'V.
I often come across in situation of determining the transient stability in BGR design as a requirement. Since the ac stability analysis only potray the small signal analysis.
Usually a Vpwl is applied to the Vdd to be ramped from 0v to Vdd, and the output is cross checked whether it settles down at the desired value, correct me if I'm wrong?. Is it the input or the Vdd is ramped. Thanks in advance
I often come across in situation of determining the transient stability in BGR design as a requirement. Since the ac stability analysis only potray the small signal analysis.
Usually a Vpwl is applied to the Vdd to be ramped from 0v to Vdd, and the output is cross checked whether it settles down at the desired value, correct me if I'm wrong?. Is it the input or the Vdd is ramped. Thanks in advance
Yes, I do agree with you that transient analyisis is the ultimate test of stability. If you get good transient response it's ok. But what if your transient analysis is bad, say, it has lot of damping etc. I mean, how will you solve this problem?
AC analysis and Phase Margin helps you here. Agreed, good Phase Margin doesn't necessarily mean good transient response. But good AC response generally does. Here, by good AC response I mean good Phase Margin, along with no zeros @UGB etc.
To cut short, Transient tells about system's stability and AC response gives control over it.
Besides AC response gives DC gain. More the gain, lower is the closed loop systematic offest. For Bandgap we need low offset.