KevinIV said:
An opamp doesn't source any current.
You are wrong, Kevin.
ALL opamps have a NPN emitter-follower at the output to source current and an PNP emitter-follower transistor at the output to sink current.
Maybe you are thinking about the output of a comparator that does not have emitter-follower outputs so it is simply an NPN open collector that sinks current but needs a pullup resistor to source current. Then the outputs of many comparators can be connected together using a single pullup resistor which makes them an OR gate.
I corrected the above because I originally got it wrong.