A voltage follower, also known as a unity gain amplifier or buffer circuit, is an electronic circuit designed to replicate the input voltage at its output while providing high input impedance and low output impedance. In other words, the voltage follower circuit has a gain of approximately 1 (unity gain), meaning the output voltage tracks the input voltage without amplification.
The primary purpose of a voltage follower circuit is to isolate or decouple one part of a circuit from another, while maintaining the same voltage level. It is often used to address impedance matching issues between different components of a circuit. Here are some key characteristics and applications of voltage follower circuits:
Characteristics:
Unity Gain: As mentioned, the voltage follower has a gain of 1. This means that the output voltage is equal to the input voltage, and there is no amplification or attenuation.
High Input Impedance: The input impedance of a voltage follower is typically very high, which means it draws minimal current from the input signal source. This helps prevent loading effects and signal degradation.
Low Output Impedance: The output impedance of a voltage follower is very low, making it capable of driving low impedance loads without significant signal loss.
Applications:
Impedance Matching: Voltage followers are often used to match the impedance between a signal source and a load. This is especially useful when the source has a high output impedance and the load requires a low input impedance, ensuring efficient transfer of the signal.
Buffering: In cases where a signal source cannot drive a load directly due to its limited current capability, a voltage follower can be inserted to act as a buffer. It isolates the source from the load and provides the necessary current drive to the load.
Voltage Isolation: Voltage followers can provide isolation between two circuits or stages that have different reference voltages. By using a voltage follower, the input and output voltages remain the same, but they are effectively isolated from each other.
Feedback Networks: Voltage followers are often used in feedback networks of operational amplifier (op-amp) circuits to provide isolation between different stages of the circuit while maintaining the desired feedback characteristics.
Signal Conditioning: In sensor applications, a voltage follower can be used to condition signals from sensors with high output impedance, ensuring minimal signal distortion and accurate measurement.
Instrumentation Amplifiers: Voltage followers are sometimes incorporated into instrumentation amplifier circuits to provide a high input impedance and low output impedance, contributing to accurate signal amplification.
In summary, a voltage follower (buffer) circuit is a versatile building block in electronics that helps address impedance matching, signal isolation, and buffering challenges in various applications. Its ability to faithfully reproduce an input signal with minimal distortion makes it a valuable tool in circuit design.