Opamps have a very high intrinsic gain, something in the order of
150,000 & higher; this is called the open loop gain. This gain is not
very useful by itself since it is very unstable; it changes with
temperature, supply voltage & also requires extremely small signals to
work within a useful range of voltages without clipping the incoming
signal.
A method deviced from the conception of the opamp is the use of a
feedback loop to limit the gain of the op amp to lower than 100, but
that the gain will only depend on external components instead of the
built in properties of the device.
The feedback is connected in a way such that any increase in the
feedback signal will lower the output, similar to adding a negative,
hence it's name.
