Buffer

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It should be noted that the operational amplifier is an active component and that it has a low output impedance. Namely that he will be able to behave like a source of tension.

 This is useful when you apply a voltage with low load carrying capacity as input. We will speak of a "buffer" stage.it is designed to allow impedance matching between two successive stages of a circuit.

Of course, this does not go without modification of the input signal: it is therefore necessary to be careful with the offset introduced by the AOP, the distortion that it will insert on the input signal, its band gain product and thus its be able to correctly pass high frequency signals,Note that the input and output are not reversed.


Linear applications

1) Voltage follower amplifier

Follower op amp

b) formula

Vout = Vin

c) Remarks

The resistance at the input of the assembly is infinite.

The voltage follower makes it possible to take a voltage without disturbing it, because it has a zero input current.

This circuit has this name because it does nothing on the voltage (the input is equal to the output), it allows the adaptation of voltage impedance:

In the example below, the simple divider bridge, and the divider bridge equipped with an op amp mounted as a follower have the same no-load output voltage. However, the output impedance (equivalent Thévenin generator impedance) of the divider bridge is R1//R2, while that of the AOP assembly is zero with the ideal op amp model.



The above results are valid as long as the output voltage Vout is between (E+ sat) and (E− sat) .


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