devrimaksin
Joined: 13 Oct 2004
Posts: 93
Helped: 9
Location: Dallas, Texas, USA
|
 26 Oct 2004 19:22 How to measure VIH and VIL (ac) in Hspice? |
|
|
|
There is no such definition,
You might be confusing propagation
delay and VIH.
When you apply a signal at the input
it takes for a while for the output to respond,
But at the same time if you keep increasing the
input, you might think that the input value at the time of output signal is changing state is VIH and/or VIL, this is not true. The problem is simply, at lower level of signal (or when you get closer to the margins), it takes longer for the circuit to response. That is why WIH and WIL are defined DCwise and not AC wise, equivalently, if you have a huge capacitor load at the output, you will see the same effect. So VIH and VIL is constant and determined by the DC analysis, but propogation delay is not and it is a function of the circuit load, input signal level and sizing and biasing
|
|
