Re: Operational Amplifier
The operational amplifier (opamp) has this name because it is a circuit element that can easily be used to perform mathematical operations with the electrical signals (addition, subtraction, multiplication, division, integration, differentiation,…).
An opamp is a circuit which, ideally, has:
-> no input current - infinite input impedance
-> infinite voltage gain
-> zero output impedance
Real opamps can present a small input current (this depends on the type of transistor used in the input), a very large gain and a small output impedance.
There are lots of materials that you can access that explain how the properties I mentioned above can be utilized to design useful circuits.
PS: Input current does not have anything to do with achieving high voltage gain. The input current is just a non-ideality. “Differential situation”, whatever that is, is also not related to the input current.