I have taken 5v from arduino and interface to input 1 of uln2003 and 9v to com 9 pin ,not getting output at 9v at 16 pin output of 1 input
That’s normal, there are diodes inside the uln2003 preventing current from flowing from pin 16 to pin 1.
What are you trying to do?
ULN2003/2803 cannot provide an output voltage.
ULN2003 outputs are only designed to sink current from a device powered from a higher voltage down to Ground.
9V to LED anode, LED cathode to resistor, other side of resistor to ULN2003 output. ULN2003 Gnd goes to Gnd.
COM would be useful if the coil of a relay was connected in place of the LED. The internal diode from output pin to COM protects the output transistor when the coil current is shut off (similar to placing a Diode across a motor).
See page 2.
uln2803a.pdf (378 KB)