A voltage follower, also known as a buffer circuit, is an electronic circuit configuration that is used to isolate or separate two parts of a circuit while maintaining the same voltage level. It's often implemented using an operational amplifier (op-amp) and is characterized by its high input impedance and low output impedance. The primary purpose of a voltage follower is to prevent loading effects on the source circuit while providing a low-impedance output that can drive subsequent stages or loads without significant voltage loss.
The basic structure of a voltage follower circuit consists of an operational amplifier with its inverting input (usually denoted as "-" or "inverting" input) connected to its output and the non-inverting input (usually denoted as "+" or "non-inverting" input) connected to the input signal source. The output of the op-amp is then fed back to its inverting input, creating a feedback loop.
Key characteristics and uses of a voltage follower circuit:
High Input Impedance: The input impedance of a voltage follower is very high, often in the megaohm range, which means it draws minimal current from the source circuit. This prevents loading effects on the source and ensures that the voltage across the source is not significantly affected.
Unity Gain: A voltage follower provides a gain of approximately 1 (unity gain). This means that the output voltage closely follows the input voltage. Mathematically, Vout = Vin.
Low Output Impedance: The output impedance of a voltage follower is low, allowing it to drive subsequent stages or loads with minimal voltage drop. This makes it useful for driving low-impedance loads or transmission lines without significant signal degradation.
Isolation: The voltage follower provides isolation between the input and output circuits, preventing the characteristics of the load from affecting the behavior of the source circuit.
Uses:
Signal Amplification and Conditioning: In cases where you need to isolate a signal source from the following circuitry while maintaining the original signal amplitude, a voltage follower can be used.
Impedance Matching: When the output impedance of a source is high and needs to be matched to a load with a lower impedance, a voltage follower can act as an impedance buffer.
Buffering in Sensor Applications: Voltage followers are commonly used with sensors that have high output impedance. They ensure that the sensor's signal is accurately transmitted to subsequent processing stages.
Active Filters: Voltage followers can be used in the feedback path of active filter circuits to maintain signal integrity while adjusting the filter characteristics.
Isolation between Stages: In audio systems or other signal processing circuits, voltage followers can separate different stages to prevent interactions between them.
In summary, a voltage follower (buffer) circuit is a crucial component in electronics, serving to maintain signal integrity, prevent loading effects, and isolate circuit stages while passing on the input voltage without amplification or distortion.