74LS245 vs 74HCT245 ?

Discussion in 'General Electronics Chat' started by CVMichael, Apr 17, 2011.

  1. CVMichael

    Thread Starter Senior Member

    Aug 3, 2007
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    Last edited: Apr 17, 2011
  2. Audioguru

    New Member

    Dec 20, 2007
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    The output high voltage of a high speed Cmos 74HCT245 is 5.0V.
    The output high voltage of a TTL 74LS245 is only about 2.7V to 3.5V.
    The IC it drives might need a minimum input high voltage of 3.5V, look it up.
     
  3. nomurphy

    AAC Fanatic!

    Aug 8, 2005
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    The 'T" in HCT means TTL compatible.
     
  4. CVMichael

    Thread Starter Senior Member

    Aug 3, 2007
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    What about differences in speed?
     
  5. nomurphy

    AAC Fanatic!

    Aug 8, 2005
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    It should be okay, the LS part will use more power.

    The schematic is kind of fuzzy for me, but it seems to me that the OE pin is floating and that only one of the three output signals has a corresponding input?
     
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