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74c14 sub

Discussion in 'Electronic Repair' started by yhan, Mar 28, 2006.

  1. yhan

    yhan Guest

    hi everyone,

    i am assembling a capacitance tester using ic 74c14 schmit trigger. The
    available IC in my box is 74HC14N. The question is, can I use 74HC14N
    as a substitute instead of 74c14?

    thanks in advance,
    ian
     
  2. yhan

    yhan Guest

    ps. according to the datasheet, 74HC14N is Hex Inverting Schmitt
    Trigger and 74C14 is Hex Schmitt Trigger.
     
  3. Guest

    Yes, you can. It's the number 7414 which tells the purpose of the chip.
    The C-letter means it is cmos-type (and it needs to be in your circuit,
    as you mentioned), and H means it is high-speed-type. It is not
    mentioned to be necessary in your circuit, but it is ok to use the
    high-speed type, although not necessary.
    Both ones are inverting. There are mistake, or maybe the maker of the
    datasheet of the 74C14 has considered the "invertingness" a "special
    feature" which wouldn't be necessary to tell on the header.
     
  4. Gerard Bok

    Gerard Bok Guest

    While you are right with the 'general picture' that it is the
    function that counts, you may well be wrong here :)

    Use in a C-meter, as the poster mentioned, is likely to be
    dependant on the Schmitt trigger's threshold.
    And that is one of specs that varies between different
    technologies :)
     
  5. James Beck

    James Beck Guest

    Also, the C part can run from a higher VCC that the HC part. That might
    pose a problem if the VCC is 9V or so.

    Jim
     
  6. yhan

    yhan Guest

    thanks to replies. According to the datasheet the VCC of of C is higher
    than HC part. In the capacitance meter i am planning to make, its
    supply voltage is 12 volts but 74hc14n VCC pin max is 6 volts only.
    That might be the problem. With the transistor tester using also 74c14,
    its supply voltage is 6 volts. In this case, the 74hc14n might be
    suited as substitute but not in the capacitance meter with the supply
    voltage of 12 volts. (Because 74c14 has a Vcc ranging from 3.5-15 v but
    74hc14n only up to 6 volts). Am I right?

    tnx again,

    ian
     
  7. James Beck

    James Beck Guest

    Yes, you are right and I would not run an HC part at 6V. I never like
    to take a part right to the edge of the envelope. I'm sure they spec'ed
    in C parts for the VCC range and the trigger threshold value.

    Jim
     
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