How does a Schmidt trigger convert a noisy input signal into a clean digital output?
1 Answer
A Schmidt trigger is a type of electronic circuit that converts an analog input signal into a clean digital output signal. It is designed to eliminate noise and provide hysteresis, which means the output state will remain unchanged until the input signal crosses a certain threshold, preventing rapid toggling when the input signal is near the threshold.
Here's how a Schmidt trigger works to convert a noisy input signal into a clean digital output:
Thresholds: A Schmidt trigger has two threshold levels: a high-level threshold (Vhigh) and a low-level threshold (Vlow). These thresholds determine when the output state switches between HIGH and LOW. Vhigh is higher than Vlow.
Positive Feedback (Hysteresis): The key feature of a Schmidt trigger is its positive feedback mechanism. Positive feedback means that the output of the circuit is fed back to its input with the same polarity. This causes the threshold levels to shift dynamically based on the output state.
Input Comparison: When the noisy analog input signal is applied to the Schmidt trigger, the circuit compares the input voltage level with the two thresholds, Vhigh and Vlow.
Clean Digital Output: If the input signal rises above Vhigh, the output switches to a HIGH state. If the input signal falls below Vlow, the output switches to a LOW state. This output state remains unchanged even if the noisy input signal fluctuates around the threshold due to the positive feedback.
Hysteresis Effect: The positive feedback introduces hysteresis in the response of the Schmidt trigger. When the output is in a HIGH state, the threshold Vlow is temporarily raised, making it harder for the input signal to bring the output back to LOW. Similarly, when the output is in a LOW state, the threshold Vhigh is temporarily lowered, making it harder for the input signal to bring the output back to HIGH. This prevents the output from toggling rapidly if the input signal is close to the threshold levels, reducing the effect of noise.
By using hysteresis and dynamically adjusting the thresholds, a Schmidt trigger effectively cleans up the noisy input signal and provides a stable and clean digital output that is less susceptible to fluctuations near the threshold levels. It is commonly used in digital systems to interface with analog signals and provide robust switching behavior in the presence of noise.
Here's how a Schmidt trigger works to convert a noisy input signal into a clean digital output:
Thresholds: A Schmidt trigger has two threshold levels: a high-level threshold (Vhigh) and a low-level threshold (Vlow). These thresholds determine when the output state switches between HIGH and LOW. Vhigh is higher than Vlow.
Positive Feedback (Hysteresis): The key feature of a Schmidt trigger is its positive feedback mechanism. Positive feedback means that the output of the circuit is fed back to its input with the same polarity. This causes the threshold levels to shift dynamically based on the output state.
Input Comparison: When the noisy analog input signal is applied to the Schmidt trigger, the circuit compares the input voltage level with the two thresholds, Vhigh and Vlow.
Clean Digital Output: If the input signal rises above Vhigh, the output switches to a HIGH state. If the input signal falls below Vlow, the output switches to a LOW state. This output state remains unchanged even if the noisy input signal fluctuates around the threshold due to the positive feedback.
Hysteresis Effect: The positive feedback introduces hysteresis in the response of the Schmidt trigger. When the output is in a HIGH state, the threshold Vlow is temporarily raised, making it harder for the input signal to bring the output back to LOW. Similarly, when the output is in a LOW state, the threshold Vhigh is temporarily lowered, making it harder for the input signal to bring the output back to HIGH. This prevents the output from toggling rapidly if the input signal is close to the threshold levels, reducing the effect of noise.
By using hysteresis and dynamically adjusting the thresholds, a Schmidt trigger effectively cleans up the noisy input signal and provides a stable and clean digital output that is less susceptible to fluctuations near the threshold levels. It is commonly used in digital systems to interface with analog signals and provide robust switching behavior in the presence of noise.