Voltage follower
This is the simplest conceivable example of a negative-feedback opamp circuit.
In the (normal) case of a large open-loop gain of the opamp (typically >100 dB)
the very direct feedback connection will force the voltage difference
between the input terminals to be virtually zero.
In this limit the closed-loop amplification factor of the circuit will thus equal unity.
Turn on the voltage source and check the circuit for different values of the open-loop gain:
>100 dB (very large gain),
20 dB (A = 10),
6 dB (A = approx. 2),
0 dB (A = 1).
Also try in some of the cases to provoke a saturation of the opamp
by application of an excessive (positive or negative) input voltage.
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About Javalab opamps