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I'm trying to test ULN2803 with Led MATRIX. But with different Logic it is giving no change on the output and making the LED lit up. Why is this soenter image description here

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  • \$\begingroup\$ It's a simulation model misbehavior and you should add pull up resistors to the outputs (for the simulation only) to correct it. Please refer to my reply electronics.stackexchange.com/a/98982/33841 \$\endgroup\$ – alexan_e May 11 '15 at 7:53
  • \$\begingroup\$ Yes this is the Right answer but how can i reference yours \$\endgroup\$ – Terminator May 19 '15 at 3:44
  • \$\begingroup\$ I have posted the solution as an answer \$\endgroup\$ – alexan_e May 19 '15 at 6:50
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It's a simulation model misbehavior, you should add pull up resistors to the outputs (for the simulation only) to correct it.

enter image description here

The shown schematic is valid for simulation only, the pullup network is not needed in the real circuit.
You also have to add the current limiting series resistors for the leds of the dot display in the real circui, they are omitted in proteus to improve the simulation speed.

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Try connecting pin 9 to 0V: -

enter image description here

You don't appear to have a pin 9 on your model?

Current limit resistors are needed for each LED segment although this is only a simulation.

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  • \$\begingroup\$ In Proteus devices the supply pins of IC are hidden (that is why you can't see then in the given schematic) and are automatically connected to the global power rails. \$\endgroup\$ – alexan_e May 11 '15 at 13:16

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