Explain the operation of a monostable multivibrator (one-shot) circuit.
1 Answer
A monostable multivibrator, also known as a one-shot circuit, is a type of electronic circuit that generates a single, fixed-duration pulse in response to an external trigger signal. This circuit has one stable state and is triggered to temporarily switch to an unstable state before returning to its original stable state after a predetermined time period.
The primary components of a monostable multivibrator circuit typically include:
Trigger Input (T): This is the external signal that initiates the operation of the circuit. It can be a voltage pulse, a button press, a sensor signal, or any other input that causes the circuit to trigger.
Threshold Input (THR): This input is connected to a voltage reference level. It determines the voltage level at which the circuit transitions from its unstable state back to its stable state.
Control Voltage (CV): This voltage is used to set the duration of the output pulse. By changing the control voltage, you can adjust the duration of the generated pulse.
Output (Q): This is the pulse output of the circuit. It remains in its stable state until triggered, at which point it transitions to the unstable state and generates a pulse before returning to the stable state.
The operation of a monostable multivibrator circuit can be explained as follows:
Stable State (Idle): Initially, the circuit is in its stable state, with the output Q at one voltage level (usually high) and the trigger input T at another voltage level (usually low). The circuit is at rest, and the output is not generating any pulses.
Triggering: When the trigger input T transitions from the low voltage level to the high voltage level (for example, due to a button press or a sensor detecting an event), the circuit is triggered. This causes the output Q to transition to the opposite voltage level (usually low), putting the circuit into an unstable state.
Unstable State (Pulse Generation): The circuit remains in this unstable state for a fixed duration determined by the components of the circuit, primarily by resistors and capacitors. During this time, the output Q stays at the low voltage level, generating a pulse. The duration of this pulse is calculated using the formula: Pulse Width (T) = 1.1 * R * C, where R is the resistance and C is the capacitance in the timing components of the circuit.
Return to Stable State: After the fixed duration (pulse width) has elapsed, the circuit transitions back to its stable state. This transition is triggered by the voltage at the threshold input THR, which typically involves comparing the voltage across a capacitor to the threshold level. When the voltage across the capacitor reaches the threshold, the output Q transitions back to its original high voltage level, ending the pulse generation.
In summary, a monostable multivibrator circuit generates a single output pulse of fixed duration in response to an external trigger input. This type of circuit is commonly used in applications such as pulse generators, time delay circuits, and debouncing circuits.
The primary components of a monostable multivibrator circuit typically include:
Trigger Input (T): This is the external signal that initiates the operation of the circuit. It can be a voltage pulse, a button press, a sensor signal, or any other input that causes the circuit to trigger.
Threshold Input (THR): This input is connected to a voltage reference level. It determines the voltage level at which the circuit transitions from its unstable state back to its stable state.
Control Voltage (CV): This voltage is used to set the duration of the output pulse. By changing the control voltage, you can adjust the duration of the generated pulse.
Output (Q): This is the pulse output of the circuit. It remains in its stable state until triggered, at which point it transitions to the unstable state and generates a pulse before returning to the stable state.
The operation of a monostable multivibrator circuit can be explained as follows:
Stable State (Idle): Initially, the circuit is in its stable state, with the output Q at one voltage level (usually high) and the trigger input T at another voltage level (usually low). The circuit is at rest, and the output is not generating any pulses.
Triggering: When the trigger input T transitions from the low voltage level to the high voltage level (for example, due to a button press or a sensor detecting an event), the circuit is triggered. This causes the output Q to transition to the opposite voltage level (usually low), putting the circuit into an unstable state.
Unstable State (Pulse Generation): The circuit remains in this unstable state for a fixed duration determined by the components of the circuit, primarily by resistors and capacitors. During this time, the output Q stays at the low voltage level, generating a pulse. The duration of this pulse is calculated using the formula: Pulse Width (T) = 1.1 * R * C, where R is the resistance and C is the capacitance in the timing components of the circuit.
Return to Stable State: After the fixed duration (pulse width) has elapsed, the circuit transitions back to its stable state. This transition is triggered by the voltage at the threshold input THR, which typically involves comparing the voltage across a capacitor to the threshold level. When the voltage across the capacitor reaches the threshold, the output Q transitions back to its original high voltage level, ending the pulse generation.
In summary, a monostable multivibrator circuit generates a single output pulse of fixed duration in response to an external trigger input. This type of circuit is commonly used in applications such as pulse generators, time delay circuits, and debouncing circuits.