What is the typical input impedance of an op-amp?

An ideal operational amplifier has an infinite input impedance, which means it draws absolutely zero current from the signal source. In practical components, especially those utilizing FET (Field Effect Transistor) inputs, the input impedance is very high, often in the range of megaohms to gigaohms. This extremely high input impedance is a highly desirable characteristic. It ensures that the op-amp does not 'load down' or draw current away from the preceding circuit stage, allowing it to measure or amplify the true voltage of the input signal without altering it.