A Schmitt trigger is a type of electronic circuit used to convert an analog input signal into a digital output signal. It's specifically designed to handle noisy or fluctuating input signals and provide a well-defined digital output that changes states (from low to high or high to low) based on preset voltage threshold levels.
The Schmitt trigger is characterized by its hysteresis property, which means it has two different threshold levels: a higher threshold level (Vhigh) and a lower threshold level (Vlow). This hysteresis helps prevent rapid switching or "chatter" of the output when the input signal is near the threshold.
Here's how a Schmitt trigger works and conditions signals:
Input Signal Comparison: The Schmitt trigger compares the incoming analog signal to its two threshold levels, Vhigh and Vlow. These thresholds are typically set such that Vhigh is greater than Vlow.
Hysteresis: When the input signal rises above the Vhigh threshold, the output of the Schmitt trigger switches from a low state (0) to a high state (1). Similarly, when the input signal falls below the Vlow threshold, the output switches from a high state (1) to a low state (0). However, the key feature here is that the Schmitt trigger remains in its current state until the input signal crosses the opposite threshold level.
Noise Rejection: The hysteresis property helps reject noise or small fluctuations in the input signal that might otherwise cause rapid switching of the output. Since the Schmitt trigger remains in its current state until the input signal crosses the opposite threshold level, minor noise near the threshold doesn't lead to unnecessary state changes.
Digital Output: The output of the Schmitt trigger is a digital signal that's either at a high logic level (usually represented as a '1') or at a low logic level (usually represented as a '0'). This output can be fed into other digital circuits for further processing.
Schmitt triggers are commonly used in applications where noise immunity, signal conditioning, or signal shaping is important. They find applications in various areas, including digital logic circuits, voltage level shifting, debouncing switches, and more. By providing stable and well-defined digital outputs from uncertain or noisy analog inputs, Schmitt triggers help improve the reliability and accuracy of digital systems.