AND Gate vs NAND Gate Propagation Time

IIRC it's typically the NAND.

What generally has less propagation time. ? A 2 input AND or a 2 input NAND gate for a given series?

I might have to dig up the datasheets for this... If anybody knows offhand, let me know..

D from BC

That used to be easy to answer. Gates were made of inverting elements (common emitter/drain transistor), and were unbuffered, so the inverting functions were faster (7400 vs. 7408, CD4011 vs. CD4081). However, it soon became common to buffer the inputs and/or outputs, sometimes even with 2 stages. There's no longer any general answer. A 74LVC08 is faster than a 74LVC00.

Anybody who tells you that he knows offhand, should not be trusted :)

LOL and almost a coffee spew..

Yep. Pre- and Post-Buffering are now commonly used to "standardize" propagation times.

...Jim Thompson

Wow...I didn't know about the internal buffering spoiling the trend for NAND to have a shorter tp. I was rooting for NAND to be faster due to fewer transistors due to the already intrinsic inverting circuits to make the NAND topology.

Things change... I suppose it's always best to not skip out on checking the datasheets.

Thanks for responses everybody. D from BC

FWIW, that's pretty much what I was going to say. :-)

Cheers! Rich