PLL charge pump analysis

Discussion in 'Homework Help' started by maybeejune, Jun 1, 2015.

  1. maybeejune

    Thread Starter New Member

    Apr 23, 2015
    Hi guys, I'm currently working on a charge pump PLL for a project in my electronics class. For the PLL, we must use a charge pump for wider phase detection. I've uploaded the given charge pump schematic.

    This is what I know so far:
    I understand that M2 and M3 of the right side and all the transistors on the left side of the circuit function as current sources and that the circuit is a push-pull stage of switching between M1 and M4 of the right side. Apart from that I am having a hard time analyzing how this circuit functions, especially what the OP amp in the center does.

    Can anyone explain how this circuit functions?