LM324 hysteresis

Discussion in 'General Electronics Chat' started by banzai, Oct 26, 2014.

  1. banzai

    Thread Starter Member

    Jan 3, 2014
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    Hi guys

    Is it possible to make a comparator controller with hysteresis using an LM324 Opamp. If possible i would be very thank full if you guys could share a sample diagram on how to build a such setup.
     
  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
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  3. MrAl

    Well-Known Member

    Jun 17, 2014
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    Hello,

    Yes you can do it but it wont be extremely fast because the LM324 and similar parts are fairly slow to change their output. Typical slew rate is 0.5v/us so if your output has to change from 0 to 10v it will take at least 20us to do that, and another 20us back down from 10v to 0v. This is also true going from -5v to +5v, and if it has to go from -10v to +10v it will take 40us.
     
  4. MrChips

    Moderator

    Oct 2, 2009
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    To add hysteresis, add a resistor (e.g. 1MΩ) from the output to the non-inverting input.
     
  5. banzai

    Thread Starter Member

    Jan 3, 2014
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    I am connecting a MOSFET to the LM324 output with a 10K pull down resistor, wouldn't that effect the R3 ?

    PS

    Switching speed is not a problem as i am building a simple temperature controller.
     
  6. #12

    Expert

    Nov 30, 2010
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  7. wmodavis

    Well-Known Member

    Oct 23, 2010
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