This is a CMOS D Flip flop courtesy Razavi.



The circuit is made up of NOR gates.

But if you try to work out by pen and paper when Reset is 0 and CK is 1 you will find you can't really find out what Q is. Does this circuit need some additional star-up circuitry?


Update : If I combine two of these circuits in the form of a phase frequency detector as shown below, the circuit works correctly. How is this happening?

@AnilReddy



How about now?