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Basic problems with a ULN2803A

Discussion in 'Electronic Basics' started by Conrad, Robert, Jan 15, 2004.

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  1. I setup my ULN2803A on a bread board with Ground grounded, and Common
    powered to 9V. When ever I wire pin 1 to a 5V source I am getting .653V on
    the output (pin 18) same with all the other pins. I can not get the chip to
    provide any more voltage than that. What could be the cause of this?
  2. hamilton

    hamilton Guest

  3. Okay, so Im an idiot.. like 5 minutes after posting that I realized that I
    was misunderstanding what I should be expecting to see. (I assumed that in
    the off state the output would be roughly common voltage (so the voltage
    across the load would be 0V)

    Though, what second drawing? My book has the pinout and then the electrical
    characteristics chart.
  4. hamilton

    hamilton Guest

    Well you did not post your data sheet, so I posted one for everyone to see.

    So, in this data sheet I posted, page 2 lower drawing shows an open
    collector circuit ( this is the point). Also shown in this schematic is
    a doide connect to all 8 open collectors in the package. This diode is
    for the flyback effect of relays. I am sure others here can find other
    uses for this diode.
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