Re: TTL specs

74XX vs 74LSXX, 74XX takes up to ten times the drive current and provides
as mush as ten times the drive current as 74LSXX. Thus a 7411 is not always
a good sub for a 74LS11, unless the inputs to the 7411 do not drive
anything else. The outputs of the 7411 will easily drive whatever the LS11
drove.

The other difference is timing, the 74LSXX have a "snappier" response to
input signals, responding faster than the 74XX stuff. As I recall they also
have a slightly faster propagation throughput, in other words the data
flows faster through the IC.

So, I would tend to not replace 74LSXX with 74XX unless I was really sure
that the circuit doesn't care enough to matter.

John :-#)#

At 04:36 PM 9/29/01, you wrote:
>Hi all,
>Once again I may be in over my head, this time with TTL ICs. On the Red
>Baron board I've been working on, someone has substituted a DM7411N for the
>74LS11 at J9. Philips or Signetics apparently made these chips, and the data
>sheet that covers both is at:
>http://www.freetradezone.com/dc_images/41/61/D0194161.pdf.
>The 7411 seems just a little slower than the 74LS11, and takes a higher
>supply current. Is the DM7411N an adequate sub for the 74LS11?
>Thanks,
>Lewis
>
>
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Received on Sat Sep 29 17:36:28 2001