How does a Schmitt trigger monostable circuit generate a single output pulse for a specific duration?
1 Answer
A Schmitt trigger monostable circuit, also known as a Schmitt trigger one-shot or simply a monostable multivibrator, is a type of electronic circuit that generates a single output pulse of a specific duration in response to an input trigger signal. It's commonly used in various applications, such as signal conditioning, pulse shaping, and timing circuits.
The circuit consists of a Schmitt trigger and a timing capacitor (C) along with some resistors. The Schmitt trigger is a comparator with hysteresis, which means it has two threshold voltage levels, one for the rising edge (upper threshold) and one for the falling edge (lower threshold) of the input signal.
Here's a step-by-step explanation of how the Schmitt trigger monostable circuit generates a single output pulse:
Idle state: Initially, the Schmitt trigger's output is in a stable state, either high or low, depending on the previous input history. For the sake of explanation, let's assume it's in a low state (0).
Input trigger: When an input trigger signal is applied to the circuit, it exceeds the rising threshold voltage of the Schmitt trigger. This triggers the Schmitt trigger to switch its output state from low (0) to high (1).
Capacitor charging: As the Schmitt trigger's output changes to high, it allows current to flow through a charging resistor (R1) and the timing capacitor (C). The capacitor begins to charge up exponentially toward the input voltage level.
Timing duration: The duration for which the output stays high is determined by the time it takes for the capacitor to charge up to the falling threshold voltage of the Schmitt trigger. This voltage level is lower than the rising threshold, and it's reached after a specific time determined by the values of the timing resistor (R1) and the timing capacitor (C).
Monostable period: During this time, the Schmitt trigger is effectively "locked" in its high state. Any additional input triggers during this period do not have any effect on the output, as the Schmitt trigger is not responsive to changes in its input until the capacitor discharges fully.
Capacitor discharging: After the specified time duration elapses, the capacitor voltage falls below the falling threshold voltage of the Schmitt trigger. This triggers the Schmitt trigger to switch its output state from high (1) back to low (0).
Output pulse: The Schmitt trigger's output returns to the stable low state, and the monostable circuit is ready to respond to the next input trigger, generating another output pulse when triggered.
In summary, the Schmitt trigger monostable circuit generates a single output pulse of a specific duration by triggering its output high when it receives an input trigger, holding it high for a predetermined time determined by the timing resistor and capacitor, and then returning the output to its stable low state after the timing period expires.
The circuit consists of a Schmitt trigger and a timing capacitor (C) along with some resistors. The Schmitt trigger is a comparator with hysteresis, which means it has two threshold voltage levels, one for the rising edge (upper threshold) and one for the falling edge (lower threshold) of the input signal.
Here's a step-by-step explanation of how the Schmitt trigger monostable circuit generates a single output pulse:
Idle state: Initially, the Schmitt trigger's output is in a stable state, either high or low, depending on the previous input history. For the sake of explanation, let's assume it's in a low state (0).
Input trigger: When an input trigger signal is applied to the circuit, it exceeds the rising threshold voltage of the Schmitt trigger. This triggers the Schmitt trigger to switch its output state from low (0) to high (1).
Capacitor charging: As the Schmitt trigger's output changes to high, it allows current to flow through a charging resistor (R1) and the timing capacitor (C). The capacitor begins to charge up exponentially toward the input voltage level.
Timing duration: The duration for which the output stays high is determined by the time it takes for the capacitor to charge up to the falling threshold voltage of the Schmitt trigger. This voltage level is lower than the rising threshold, and it's reached after a specific time determined by the values of the timing resistor (R1) and the timing capacitor (C).
Monostable period: During this time, the Schmitt trigger is effectively "locked" in its high state. Any additional input triggers during this period do not have any effect on the output, as the Schmitt trigger is not responsive to changes in its input until the capacitor discharges fully.
Capacitor discharging: After the specified time duration elapses, the capacitor voltage falls below the falling threshold voltage of the Schmitt trigger. This triggers the Schmitt trigger to switch its output state from high (1) back to low (0).
Output pulse: The Schmitt trigger's output returns to the stable low state, and the monostable circuit is ready to respond to the next input trigger, generating another output pulse when triggered.
In summary, the Schmitt trigger monostable circuit generates a single output pulse of a specific duration by triggering its output high when it receives an input trigger, holding it high for a predetermined time determined by the timing resistor and capacitor, and then returning the output to its stable low state after the timing period expires.