why is that? help~~~

hgmjr

Joined Jan 28, 2005
9,027
I believe your answer can be obtained by taking a look at any manufacturer's datasheet for an AND gate and a NAND gate. Make sure that you compare like technologies. CMOS would be a good technology to use in your investigation.

Most of them have a typical gate circuit included in their datasheets.

hgmjr
 

hgmjr

Joined Jan 28, 2005
9,027
Here are a couple of example datasheets from TI.

AND gate

NAND gate

Take a look at the typical circuit for the 7400 and the 7408 in the linked-to datasheets from TI. The reason for the difference in speed is tied to the propagation from input to output. See if you can spot why it takes longer for a signal change on the input to manifest itself on the output of these two different gates.

hgmjr
 

Thread Starter

katherine1117

Joined Oct 28, 2009
9
Here are a couple of example datasheets from TI.

AND gate

NAND gate

Take a look at the typical circuit for the 7400 and the 7408 in the linked-to datasheets from TI. The reason for the difference in speed is tied to the propagation from input to output. See if you can spot why it takes longer for a signal change on the input to manifest itself on the output of these two different gates.

hgmjr
i'm still not quite sure, can you explain it further? thx very much
 
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