Flip-flops are bistable devices. However to switch the state you need to drive the gate for a finite time. If your input is short, the output will revert back to the original state. Thus we need hold time to successfully switch the state. for setup time, After you apply the input signal it takes some time to charge/discharge the input capacitors. Before that the input nodes will have wrong voltages. Thus set-up time is required to fully prepare the input for sampling...Hi Swapnil_vlsi what u told is defination of setup and hold time.
my question is theory behind Tsu and Th.
Tsu needs to charch the cepacitor ..
next Q. is why Th is requored...