question about transistor resistor logic

Discussion in 'Homework Help' started by caoadon, Aug 11, 2014.

  1. caoadon

    Thread Starter New Member

    Jul 11, 2014
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    Can an inverter logic gate invert a high frequency pulse? (1MHz)

    thanks
     
  2. MrChips

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    Oct 2, 2009
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    Why not?
    7404 TTL inverters are good to at least 25MHz.
     
  3. alfacliff

    Well-Known Member

    Dec 13, 2013
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    but RTL inverters are a lot slower.
     
  4. caoadon

    Thread Starter New Member

    Jul 11, 2014
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    Oh could i use a 7404 for just a single input and output? there are so many pins
     
  5. caoadon

    Thread Starter New Member

    Jul 11, 2014
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    nvm dumb question. but thanks i'll look into buying a TTL
     
  6. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Each gate is independent of all others. Just use one.
    Or.
    Buy chip that only has one gate, and meets your frequency requirement.
     
  7. MikeML

    AAC Fanatic!

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    Make your own: one NPN transistor and two resistors...
     
  8. caoadon

    Thread Starter New Member

    Jul 11, 2014
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    are there two optimal resistors i can use? I've seen so many variations of it
     
  9. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Depends on input voltage and current, and desired output voltage and current.
     
  10. caoadon

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    Jul 11, 2014
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    5V pulse with a max current of 400μA?
    I just want an exact inversion of it.
    Sorry I can't think of the math right now...
     
  11. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    In retrospect, the 400uA makes it tough to do with a simple NPN (or with TTL or even LSTTL), I would use a 4000 series CMOS inverter.
     
  12. MrChips

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    Oct 2, 2009
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    You can get single gate components in a SMD package.

    Or go with a single NPN transistor with two resistors as shown here:

    [​IMG]

    The voltage source can be +5V instead of the +12V shown.
     
  13. caoadon

    Thread Starter New Member

    Jul 11, 2014
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    i just bought an NTE7404 hex inverter. Do i need to use resistors with them?
     
  14. MrChips

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    Oct 2, 2009
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    No need for additional resistors for your application.
    You can use a single gate and leave the remaining five not connected.
    If you want extra output power you can parallel multiple gates together.

    400μA could be a limiting factor. Try it with one gate first and see what happens.
     
  15. caoadon

    Thread Starter New Member

    Jul 11, 2014
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    It seems to be inverting fine. Do I not need to do impedance matching? THeres a 50ohm input impedance.
     
  16. MrChips

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    Where exactly is the 50-ohm impedance?
     
  17. caoadon

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    Jul 11, 2014
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    The ultrasound im working with outputs a signal that i want to invert. so i sent it through the hex inverter. once inverted, the output of the hex inverter is the input of a laser with a 50ohm input impedance
     
  18. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    So this is an analog signal? If so, you need a medium fast modern opamp to invert the signal while retaining its fidelity; not a logic inverter...
     
  19. MrChips

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    Oct 2, 2009
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    Perhaps you should go into more details as to what you are attempting to do.
     
  20. caoadon

    Thread Starter New Member

    Jul 11, 2014
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    I am trying to invert a pulse and input it into a laser. The laser has a 50ohm input impedance.

    I just bought a 7406 hex inverter open collector.
    The 7404 didn't work. or it didn't invert the signal exactly (it was around a 2V pulse compared to the original 5V) because of the 50ohm impedance.
     
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