View Full Version : problem using ULN2803A

07-24-2009, 11:36 PM
Hi all,
I am using ULN2803A but it isnt wrkng as i expctd.
i have connected pin 9 to ground.
and when i give a high at pin1 i recieve a low at pin18

and when i give a low at pin1 i recieve nothing at pin18.

as expctd it should amplify the voltage at around 12v. but it isnt doing so

07-24-2009, 11:42 PM
@htsh_shrm: The ULN is a darlington transistor(NPN) array. It sinks current. If you need to source the current, you should look at the UDN2982 (PNP).


Debu :)

07-25-2009, 11:53 PM
The 2803 is NOT a logic gate!!!

Have you connected a Load resistor at the output????

08-03-2009, 11:23 PM
thnx everybody out here......... i am done with ULN2803A. it worked perfectly.
and now am using a 5V Relay, so i dont need it now... direct connection from my microcontroller with a freewheeling diode works perfectly

08-18-2009, 12:52 AM