Folded cascode toplology

Discussion in 'General Electronics Chat' started by anhnha, Jan 16, 2016.

  1. anhnha

    Thread Starter Active Member

    Apr 19, 2012
    Here is a folded cascode amplifier. There are two problems that I am confused. Hope anyone can
    come up with an answer.
    1. Why the small signal current gm1*Vin flows from NMOS to PMOS not in the opposite direction?
    2. There seems to be a contradiciton here. The current flows through M2 is always a constant (I2).
    However, there is a small signal current gm1*Vin that is varying flows through it.
    How is it possible for the PMOS current constant?

    Folded cascode topology.PNG