A voltage follower, also known as a buffer circuit, is a simple electronic circuit that is designed to replicate the input voltage at its output while providing high input impedance and low output impedance. In other words, it mimics the input signal without amplifying or attenuating it. The primary purpose of a voltage follower is to isolate or decouple a source from the load, ensuring that the load impedance doesn't significantly affect the source and vice versa.
The basic configuration of a voltage follower circuit consists of an operational amplifier (op-amp) with its inverting input connected to its output and its non-inverting input connected to the input signal source. The op-amp amplifies the difference between its inputs, but in this case, the output is connected directly to the inverting input, creating a unity gain configuration.
Key characteristics and uses of a voltage follower (buffer) circuit include:
Impedance Matching: Voltage followers are commonly used to match the impedance between a source and a load. If the output impedance of the source is high and the input impedance of the load is low, connecting them directly would lead to signal loss due to voltage division. By inserting a voltage follower between them, the high input impedance of the voltage follower effectively isolates the source from the load, preventing signal degradation.
Signal Isolation: In some cases, you might want to isolate the source from the load to prevent loading effects. A voltage follower can act as an isolation barrier, ensuring that the load doesn't disturb the source.
Amplifier Matching: When connecting different stages of amplification, the output impedance of one stage might not match the input impedance of the next stage. Using a voltage follower in between can help prevent signal loss and distortion that could occur due to impedance mismatch.
Voltage Level Shifting: Sometimes, you might need to shift the DC level of a signal. A voltage follower can be used for level shifting by biasing its input with a DC voltage and then applying the desired AC signal on top of it. The output will replicate the AC signal while being centered around the DC bias voltage.
Buffering Weak Signals: Weak signals with high source impedance can suffer from significant attenuation when connected to low impedance loads. A voltage follower can buffer such signals and ensure they are delivered to the load without distortion.
Instrumentation and Measurement: In measurement and instrumentation systems, voltage followers can help maintain the fidelity of the measured signal by isolating the measurement equipment from the signal source.
In summary, a voltage follower (buffer) circuit is a fundamental component in electronics that serves to replicate an input voltage at its output while providing impedance matching and isolation benefits. It's widely used in various applications to ensure that signals are transmitted accurately and without degradation between different parts of a circuit.