In Digital Electronics, what's 'propagation delay'?

Question

i'm studying for the RIT DE exam tommorrow, so any help would be beneficial. thanks. Also, if known, what's the advantage of CMOS gates over TTL gates?

Answer 1

Real devices have associated with them a parameter called "propagation delay" which is a measure of the time delay between arrival of a correct clock/trigger condition and any observable change in output.

The timing diagrams you draw in class, are for devices which have no propagation delay since as soon as a input is detected the output changes but that is not the case in the real world, were it takes a few nanoseconds for a device to switch states when it recieves a input signal.

Answer 2

Propagation Delay In Digital Electronics

Answer 3

Advantage CMOS vs TTL gates:
-CMOS: Can tolerate wide input power eg: 2~6V but TTL 5V+/-10%.
-consume less power than TTL at frequency less than 1MHz.
-higher speed than TTL
Disadvantage: sensitive to static charge

Answer 4

Propagation delay is the time delay between the input signal and the output result. That's it.

Answer 5

The other guys didn't answer the CMOS/TTL thing.

CMOS wins out in low power consumption, almost nothing when not being clocked and being unfussy about the supply voltage.

It loses out in speed and drive ability (fan out).

Answer 6

How long it takes for a signal to propagate from input to output in a digital logic stage.