hello:
to getting amplification of 4017 counter outputs i use 10 trs 2n2222 . now i ask if we can replace 8 trs with an ic uln 2803 (have 8 transistors array)
thanks

 

I think so, but I can't be sure without any datasheets or a diagram of how YOU are building the circuit.

 

ULN2804 would be a better match, as it has 10.5k Ohm resistors on the input instead of 2.3k like the '2803's.