General Engineering Terms
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Voltage Follower

A voltage follower is a particular configuration of an operational amplifier. Primarily the voltage follower is used as a buffer between circuits. A voltage follower may also be indicated as a unity gain buffer, because the circuit provides no gain, or a gain of one and is used as a buffer. The general definition of a voltage follower is a circuit having an output that follows the input, so no gain, attenuation or phase inversion.

A voltage follower is a non-inverting amplifier, the output is a replica of the input. Note the load resistance and capacitance are shown in the circuit to represent a load and are not necessarily part of a voltage follower circuit. The voltage follower is an Op Amp with the output feed back to the negative input.

LM741 Voltage Follower with load resistor and load capacitor
Voltage Follower

So any operational amplifier could be configured into a voltage follower just by applying the input to the plus pin and connecting the minus pin to the output. The connection leads to an amplifier with a high input impedance and a low output impedance, exactly what an amplifier should have. However the input and output impedances are amplifier dependent, so using different Op Amps makes a difference in the impedance they present to the circuits their connected to. An LM741 has an input impedance of 6M ohms [6 zeros] while a TL084 has an input impedance of 10T ohms [12 zeros]. The higher the impedance, the less effect the amplifier has on the circuit driving it, making it a true buffer. All the other electrical characteristics also play a role in selecting one Op Amp over another; voltage range, power, package options and so one.

The TL084 configured as a voltage follower is used in an example of a Distribution Amplifier; with each buffer driving the identical signal to a different destination. The Lm741 was used in this example just to represent the fact that any Op Amp could fill the roll.

The LM102 and LM110 are two examples of amplifiers preconfigured as voltage follower, they each have one output and only one input, and are designed for that function. There are many other Op Amps that are pre-designed to be voltage followers; however the devices that use the term buffers may be something other than a voltage follower, and may generate gain.

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