Monostable Multivibrator

Monostable MultivibratorA monostable multivibrator also known as one-shot multivibrator is designed to generate single pulses with determined duration. Pulses shape is similar to a rectangle. Pulse generation on a multivibrator output occurs only when a trigger signal has been applied at the input terminal. Before the trigger signal has been applied, the mulivibrator is in the stable state, e.g. is waiting to be launched, that's why this mode is called the waiting mode. After the trigger signal has been applied the multivibrator switches to its unstable position. The multivibrator can't stay in this position for long and automatically reverts back to its stable state.Let's consider how a monostable multivibrator assembled on a К176LА7 microcircuit which is a common logic element, works. Let's look at the chart.In its initial state, which means in the stable state the C2 capacitor is discharged. That's why on both 1 and 2 inputs and on the output of the microcircuit the voltage is high. A short low-level signal caused by the droop of input pulse differentiates the C1R1 circuit. As a result the first element of the circuit switches to the 1 state and the second - to the zero state. Meanwhile the low-level signal that appears at the output of the second element passes through the C2 capacitor to the input of the first element and supports it in the 1 state. Simultaneously the capacitor starts charging from the voltage supplying source through the R2 resistor. As soon as the capacitor voltage reaches its threshold level the DD1.1 element will switch to the zero state. At the same time at the output of the DD1.2 element a positive voltage swing will appear and through the same C2 capacitor will pass to the input of the first element and will switch both elements of the monostable multivibrator to their initial state. The VD1 diode shown on the chart with hatches is turned on when the monostable multivibrator is to be switched to the waiting mode urgently.

Category:

Science & Technology

Tags:

• chip
• circuitry
• operating principle
• signal