Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Schmitt triggers

  1. Jul 16, 2007 #1
    Hello All,

    I was just wondering if anyone knows of a different version of the 74HC7014 Hex non-inverting Schmitt-trigger buffer chip that can run on up to 9V? This one only goes up to 6V. I know I could easily use a voltage divider or a regulator to handle it but if there is a higher voltage one out there, it would save me the extra components.

    Thanks,
    Jason O
     
  2. jcsd
  3. Jul 16, 2007 #2

    xez

    User Avatar

    The old 4000 series metal gate CMOS ICs can run on 9V;
    the 40106 part is a hex schmitt trigger input inverter chip
    similar to what you've been using.

    I imagine that digikey.com, mouser.com, newark, et. al.
    could still provide some of those parts for you.

    They run more slowly in maximum frequency than the
    newer 74HC series parts, but they're all in excess of a
    couple of MHz so you should have no trouble using it in
    your circuit.
     
  4. Jul 16, 2007 #3

    xez

    User Avatar

  5. Jul 16, 2007 #4
    Hi Xez,

    Thanks for the heads up on that. I will specifically need the Hex, non-inverting Schmitt triggers if they have them. I did my original tests using a 74LS14 IC which worked fine but I had to use some extra gates to convert the inverted logic output to the non-inverted one.

    Here's the ultimate circuit scheme I'm going for.

    Thanks,
    Jason O
     

    Attached Files:

  6. Jul 16, 2007 #5

    xez

    User Avatar

    oops I posted the previous message before I saw your
    update about wanting non-inverting.
    I'll have a look at schmitt buffers vs inverters and post
    back.

    Though you can use 2 series connected inverters
    (double inversion = no inversion) and still get 3 schmitt
    buffers per hex inverter package, if no better option is
    available.
     
  7. Jul 16, 2007 #6

    xez

    User Avatar

    I don't see any devices that will satisfy the
    7VDC supply and at least 3 non-inverting schmitt triggers
    per package. I'm sure you could use various comparators
    with external resistors, or perhaps some kind of line receiver
    with hysteresis, but those will probably be not so much
    worth the effort of finding / using as compared to just
    using the IC you've identified.

    Use a 78L05 regulator, a couple 10uF 12V electrolytic
    capacitors, and a couple ceramic 0.1uF capacitors with
    one 10uF and one 0.1uF cap paired on the regulator's
    input, and another pair on the regulator's output.

    Put a 680 ohm resistor from the regulator's output to
    ground so you'll meet the minimum load
    current requirement for the regulator.
     
  8. Jul 19, 2007 #7
    Hey,

    I was looking around and I finally found an IC that can run on 9V. It's a HEF4050. What do you think?

    - Jason O
     
  9. Jul 19, 2007 #8

    xez

    User Avatar

    http://www.nxp.com/acrobat/datasheets/HEF4050B_CNV_3.pdf
    http://www.nxp.com/#/pip/cb=[type=product,path=50808/53286/29313,final=HEF4050B_CNV_3]|pip=[pip=HEF4050B_CNV_3][0]

    It's a non-inverting logic buffer that can run on +9VDC,
    yes, but I don't see anywhere that it has built in
    hysteresis like a schmitt trigger, so it seems unsuitable.

    Perhaps I'm just not reading the same datasheets that
    you are, since it may be made by multiple vendors,
    and even nxp has other 'related' family datasheets
    that I haven't opened... or perhaps I've missed the
    mention of the hysteresis though it may be present in
    what I've looked at.
     
  10. Jul 19, 2007 #9

    xez

    User Avatar

    Hmm this bb's software really toasted that second URL
    I posted. :(

    Anyway, there likely are some interface/buffer/line receiver
    products out there that can run on 7V and which have
    hysteresis too. Maybe something else made by
    NXP, SONY, ON, MAXIM, TI, LTI, ....
     
  11. Jul 19, 2007 #10

    berkeman

    User Avatar

    Staff: Mentor

  12. Jul 19, 2007 #11

    berkeman

    User Avatar

    Staff: Mentor

    Oops, sorry. Why do you want a non-inverting buffer for a ring oscillator? I think I'm in the wrong thread..... (happens more often than I like)
     
  13. Jul 19, 2007 #12

    xez

    User Avatar

    I'm not sure myself why inversion or non-inversion would
    matter in his circuit; certainly if he's feeding it with a
    square wave, it'd be irrelevant except for the
    matter of phase polarity of output relative to the
    input signal.

    But he said he wanted non-inverting, so I presume he
    has his reasons.
     
  14. Jul 19, 2007 #13
    HI All,

    I think I had a blonde moment there when I posted that data sheet, the reason I want to use the non-inverting Schmitt buffers is to minimize the number of gates I need to use. For the circuit I posted above to work, I only need three Schmitt buffers, but if I use the inverting ones, then I'll have to use a forth one to get the signal back to the right polarity. The circuit board I'm trying to design is small so I'm trying to minimize the number of chips and traces on the board.

    - Jason O
     
  15. Jul 19, 2007 #14

    xez

    User Avatar

    I understand why it's better to use less parts/gates,
    what I meant was that I don't understand why it'd
    matter what the output polarity was at any moment
    as long as the waveform / frequency / relative phase
    to the other FET driver input channels was right.

    With a square wave input to the phase shifter and duty
    cycle changer it'd eventually produce both outputs,
    the only difference inversion would make is an additional
    180 degrees from input to output.

    What're you doing / studying with your magnetic field
    rotator anyway, just for curiosity's sake?
     
  16. Jul 20, 2007 #15
    I'm studying the effects of high velocity rotating magnetic fields on coils. There is this device known as the Steven Mark Toroidal generator which is supposed to produce anomalous effects because of a high speed rotating field so I am studying this to find out for my self what is going on.

    - Jason O
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Schmitt triggers
Loading...