74LS and 74HC Series

Discussion in 'General Electronics Chat' started by nDever, Jan 24, 2011.

  1. nDever

    Thread Starter Active Member

    Jan 13, 2011
    Hey Guys,

    Will I be able to safely drive 74LS with 74HC series ICs and/or vise versa? I have read that the logic levels are not quite the same for both series ICs because the HC series is CMOS. How different are the TTL and power consumption levels?
  2. BillB3857

    AAC Fanatic!

    Feb 28, 2009
  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
    The short answer is you can drive LS with HC, but the inverse is not true. 74HCT and 74LS are compatible in both directions. In addition, 74HC and 74HCT are compatible both ways.
    You have to be aware of fanout limitations in all cases.

    You should still read AN-319.