A voltage follower, also known as a unity gain amplifier or buffer circuit, is an electronic circuit that has an input and an output, where the output voltage directly follows the input voltage without any amplification. In other words, the voltage follower has a gain of 1, meaning that the output voltage matches the input voltage exactly in magnitude.
The basic configuration of a voltage follower circuit consists of an operational amplifier (op-amp) with a feedback loop that connects the output back to the inverting input. The non-inverting input of the op-amp is connected to the input voltage source.
Here's a simplified explanation of how a voltage follower circuit works:
When a voltage is applied to the input, the op-amp compares the voltages at its inverting and non-inverting inputs.
Since the op-amp strives to make the voltages at its inputs equal, it adjusts its output voltage in a way that the inverting input voltage matches the non-inverting input voltage.
As a result, the output voltage of the voltage follower follows the input voltage closely, creating a buffer between the input and output.
Applications of Voltage Follower (Buffer) Circuits:
Impedance Matching: Voltage follower circuits are often used to match the impedance between a source and a load. When the output impedance of a signal source is high and needs to be connected to a low-impedance load, a voltage follower can be inserted between them to prevent signal degradation.
Isolation: Voltage followers can provide isolation between two circuits by electrically separating them while maintaining signal integrity. This is particularly useful when a sensitive load needs to be isolated from a potentially noisy or high-impedance source.
Signal Conditioning: In sensor applications, voltage followers can be used to condition weak sensor signals before they are sent to subsequent processing stages. The voltage follower helps prevent loading of the sensor output and ensures that the signal characteristics remain unchanged.
Active Filters: Voltage followers can be incorporated into active filter designs to avoid loading the filter's frequency response. They help prevent changes in the filter's characteristics due to the impedance of the following stages.
Cable Driving: When transmitting signals over long cables, voltage followers can be used to drive the cable and compensate for its capacitance and resistance, ensuring that the original signal reaches the destination without significant degradation.
Current Amplification: In cases where the input current is small but the output current needs to be larger, a current buffer can be constructed using a voltage follower with a feedback resistor. This creates a buffer that maintains current consistency.
Instrumentation Amplifiers: In some precision measurement applications, instrumentation amplifiers use voltage follower configurations to provide high input impedance and low output impedance while amplifying the difference between two input voltages.
In summary, a voltage follower (buffer) circuit is a fundamental building block in electronics, often used to isolate and condition signals, match impedance, and maintain signal integrity in various applications.