Hi
in section 12.6.1 of gray and meyer book (Analysis and Design of Analog Integrated Circuits) the below text has been written:
Therefore, the poles p1d and p2d of the DM half-circuit are given by (9.32)
and (9.33). Assume that the op amp is operating in a feedback loop, the feedback factor fdm
for the DM feedback loop is frequency-independent, and the right-half-plane zero has been
eliminated. Then to achieve 45◦ phase margin, the magnitude of the DM loop gain should be
unity at the frequency |p2d|. Since |gain|×frequency is constant from |p1d| to |p2d| due to the
one-pole roll-off there, we can write
|adm0.fdm.p1d| = 1 · |p2d| (12.73)
anyone can explain to me:
1) why between p1d and p2d poles, the |gain|*frequency is constant?i know in open loop opamp in this range, gain is roll of as 20db/decade
2) the relation 12.73 how is obtained ? note that this relation is written for closed loop opamp.
thanks