PLL charge pump analysis

Thread Starter

maybeejune

Joined Apr 23, 2015
3
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?

Thanks.
 

Attachments

Top