Hi every one,
I've just read Ken Kundert's book on spice&spetre about ac simulation on feedback circuit. (section 3.4.1)
In his book, he mentioned that the most accurate way to characterize the real feedback circuit is to use two-port parameter(Y,Z,G,H), because this method naturally include all the feedback and feedforward(bi-directional) effect and loading effect into a single two-port presentation even you don't need to open your feedback loop. Once you get parameter decideded, you get all feedback infomation(open loop gain, closed loop gain).
I'm a little curious that what's the practical disadvantage of two-port parameter method, which 2 ports in real circuits should be used to extract the parameter? what about the circuit that do not have explicit input or output port (like bandgap)? Which two port parameter should be choosen for a specific circuit?
Furthermore, Middlebrook method seems to be a little bit more popular than above method, is it right?
Now I'm going to analysis the loop stability of a bandgap (circuit is seem as Khong-Meng Tham's paper, JSSC 1995 May VOL.30 NO.5 "A low Supply Voltage High PSRR Voltage Reference in CMOS Process").
I've to choose one method to characterize the feedback build-in the bandgap. Which method should I choose?
Anyone please give your opinion. thanks very much!