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Trying to identify this IC

Discussion in 'General Electronics Discussion' started by Mclambert, Apr 4, 2013.

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  1. Mclambert


    Apr 3, 2013
    Looks like switching but not sure.

    Attached Files:

  2. Electrobrains


    Jan 2, 2012
    Most probably it's a dual OP-Amp or Comparator.
    For instance (my favorite) LM358 or a more modern type:

    I just wonder is nothing else is connected to pin 2?
  3. Mclambert


    Apr 3, 2013
    Thank you so much!

    there is a diode before the switch on pin 2. would that be what you were talking about?
  4. davenn

    davenn Moderator

    Sep 5, 2009
    and if it was an op-amp as suggested in post #2
    why would you short cct the output back to the inverting input ??
    if there was any sort of feedback, then usually there would be a resistor in that path wouldnt there ??

  5. Mclambert


    Apr 3, 2013
    You got me Devenn, I think there just trying to make a complicated switch.

    I had a good laught by the way at you joke ..
    Thanks Mike.
  6. Electrobrains


    Jan 2, 2012
    That an op-amp has its output and negative input connected together is very common.
    It's called a unity-gain-amplifier (gain=1) and is used to interface high impedance circuits!

    In this case (if it's really a dual op-amp), the circuit is build so that the output current is split between the two op-amps (maybe one can not drive everything alone).

    What seems strange to me, is the resistor ladder to the left. It seems to set the resistance value with quite much accuracy towards the positive supply. Normally you would have a sensor or something else connected from pin 3 down towards ground.

    In a similar way, pin 2 would need a voltage divider or at least a pull-up resistor to work properly and compare that signal with the one on input pin 3.

    Perhaps the inputs are not normal voltage inputs, but rather current inputs!
    Or there could be internal current sourcing/sinking on those inputs.
  7. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    I doubt it's a dual op-amp. The power supply pins match, but the rest of the pin connections don't make sense. There's no point in connecting just a switch to ground to an op-amp input (pin 2). There's no signal feeding pin 3. The output of an op-amp doesn't normally have enough drive capability to power a relay coil and there is no reason to drive the top end of the coil from anything other than a power supply. The transistor that drives the coil will be expecting an on/off signal.

    I don't recognise it at all. Are there any markings on it? Even a manufacturer's logo?
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