Working of LM 393

Discussion in 'General Electronics Chat' started by rajeshsura, May 8, 2014.

  1. rajeshsura

    Thread Starter New Member

    Feb 25, 2014
    2
    0
    I gave a PWM to the input of LM393 and did not connect anything at the output. Tried probing the output pins and the o/p stays low instead of an isolated PWM. Does LM 393 require a pull up or pull down at the output...?
     
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,523
    1,247
    Pull up. The output is an open-collector. Can you post your schematic?

    ak
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,000
    3,229
    I don't understand why looking at a data sheet seems so difficult. :confused: If you look at this you will see that the output is an open collector transistor and that all the application schematics show a pull-up resistor.

    Why do you want to apply a PWM signal to a comparator? The PWM signal should already be a digital signal.
     
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