Toshiba's ULN2003a is not generating 500 milli amps of output.

Thread Starter


Joined Sep 13, 2015
I was working this darlington pair IC, as manufacturer stated it should provide output of 500 mAmps at single node. But when i tested it was generating only 4 mAmps. Everytime I test it put the current down instead of amplifying.

Why i am facing this??? Please help.
The ULN2003 is a strange beast. It only requires ground an input and an output to work. It can sink up to 500 mA which means your loads can't draw more than that.

Your load is connected to the load power supply through the output of the darlington and then to ground. The ULN2003 act as a switch to ground, not much more.

The COMMON terminal is the strange beast. It just creates the needed path for the internal relay coil suppression diodes. That's it.

The NICE part of the ULN2003 is that an unconnected input is interpreted as a LOW.


Joined Aug 23, 2012
Please Attach your circuit as 800x600 *.gif.
ULN2003 can be sink 500mA whatever single node or total are the same, but don't use it that tie, using it less than 500mA*(1/3) is better, you just think that if you have 500 dollars then you want to spend 500 or 500 * (1/3)?


Joined Nov 23, 2012
What resistors are in the path of the 5mA? What voltage is supplied to this circuit?

As said, hand draw the circuit, snap a picture and post it (unless you have a drawing from a software package- post that).


Joined Aug 1, 2013
The 2003 does not "generate" current. Typically it is used as a switch, so the current through the device is set by the external components - the rest of your circuit. If you don't post your schematic, you never will get any kind of successful answer.

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