help for lm324

Discussion in 'General Electronics Chat' started by dariush, Jul 1, 2013.

  1. dariush

    Thread Starter New Member

    Jun 25, 2013
    8
    0
    i want to test lm324 in this way:
    im using 1/4 op-amps. short circuit all other inputs(5,6,9,10,12,13) to the ground. connect 17 volt,.02 ampere to pin 4, 1k resistor to pin3 and 10 k resistor to pin2(with a same voltage sours 17 volt) and noe LED with a 1k resistor to pin one but LED doesnt lights on?why? i dont know.
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,052
    3,244
    Why would you expect it to light? You are applying the same voltage to each input, just through a different resistor value, which has little effect on the voltage due to the high input impedance of the op amp. An op amp requires a slightly different voltage applied to each input to give a defined output level. Please read a tutorial about how op amps work to understand this.

    Post your circuit diagram.
     
  3. absf

    Senior Member

    Dec 29, 2010
    1,493
    372
    If you put another 10K on pin2 to negative of the 17V. Then the LED would light.

    See schematic.

    Allen
     
  4. w2aew

    Member

    Jan 3, 2012
    219
    64
    You might want to view my video tutorial on the basics of op amp circuits:
    http://www.youtube.com/watch?v=K03Rom3Cs28
     
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