What does it mean that an op amp has a high input impedance.. in laymans terms…why is it so important?
It means that the OP amp will draw very little current from the source that feeds it and thus have little if any loading effect on that source. Because of it`s high input impedance the OP amp`s input can be from a source that has a high output impedance such as a transistor. I do not agree with responder noplate`s statement that impedance is just a fancy word for resistance. I also disagree with responder Paul F`s assumption that impedance is the same as AC resistance. Capacitive reactance and inductive reactance are both an impedance expressed in ohms but neither contains any AC or DC resistance.