A Schmitt Trigger is a comparator circuit or device that incorporates a feedback system such that it responds to two comparator thresholds instead of one. Its dual-threshold property as a comparator allows it to be more resistant to input noise and achieve a more stable output.
Just like other multivibrator circuits, its output can have two possible states - 'low' and 'high'. When the input exceeds the higher threshold, the output goes to 'high'. On the other hand, the output goes to 'low' when the input goes below the lower threshold. The output retains its current level if the input is in between the two thresholds.
The circuit got its name from its inventor, US scientist Otto Schmitt. It is called a trigger because the output doesn't change until the change in input is large enough to 'trigger' a reversal in the level of the output.
The fact that the Schmitt trigger responds to two input thresholds and exhibits an output that depends on the 'history' of the input implies that the circuit has some memory. This phenomenon is also known as 'hysteresis', which is defined as the dependence of an output signal upon the history of prior inputs and the direction of the current traversal of the input.
An ordinary comparator has only one input threshold, i.e., its output is high if the input is greater than this threshold and low if the input is lower than this threshold. If the input is hovering close to this threshold, a small amount of input noise can make the input oscillate between the two sides of the threshold, causing the output to oscillate between 'high' and 'low' as well. A Schmitt trigger is immune to this problem, since its dual-threshold property requires a larger input swing to switch the state of the output.
The Schmitt trigger is widely used in cleaning up or conditioning a signal for digital use, or in improving digital transitions from low to high and vice versa. For example, a noisy periodic analog signal can be turned into a clean pulse train by feeding it into a Schmitt trigger.
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A Schmitt Trigger is a comparator circuit or device that incorporates a feedback system such that it responds to two comparator thresholds instead of one. Its dual-threshold property as a comparator allows it to be more resistant to input noise and achieve a more stable output.
Just like other multivibrator circuits, its output can have two possible states - 'low' and 'high'. When the input exceeds the higher threshold, the output goes to 'high'. On the other hand, the output goes to 'low' when the input goes below the lower threshold. The output retains its current level if the input is in between the two thresholds.
The circuit got its name from its inventor, US scientist Otto Schmitt. It is called a trigger because the output doesn't change until the change in input is large enough to 'trigger' a reversal in the level of the output.
The fact that the Schmitt trigger responds to two input thresholds and exhibits an output that depends on the 'history' of the input implies that the circuit has some memory. This phenomenon is also known as 'hysteresis', which is defined as the dependence of an output signal upon the history of prior inputs and the direction of the current traversal of the input.
An ordinary comparator has only one input threshold, i.e., its output is high if the input is greater than this threshold and low if the input is lower than this threshold. If the input is hovering close to this threshold, a small amount of input noise can make the input oscillate between the two sides of the threshold, causing the output to oscillate between 'high' and 'low' as well. A Schmitt trigger is immune to this problem, since its dual-threshold property requires a larger input swing to switch the state of the output.
The Schmitt trigger is widely used in cleaning up or conditioning a signal for digital use, or in improving digital transitions from low to high and vice versa. For example, a noisy periodic analog signal can be turned into a clean pulse train by feeding it into a Schmitt trigger.
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