akbarza
Full Member level 2
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
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
