Introduction:
A multivibrator circuit is one that keeps oscillating between two states HIGH and LOW. Astable, which means a circuit that oscillates between unstable states. An Astable multivibrator is a type of transistor switching circuit, which has no output stability which means it keeps on changing its state from HIGH to LOW. This type of multivibrator works without any triggering pulse and is therefore also known as the free-running multivibrator. The output obtained is a square wave from the Astable multivibrator.
A 555 timer IC can be used to build an Astable multivibrator circuit by adding three external components that are two resistors and a capacitor. The 555 timer IC generates time delays which can help in switching between the HIGH and LOW states. This post explains the circuit diagram and working of the Astable multivibrator circuit.
Hardware Components
The following components are required to make Astable Multivibrator Circuit
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | IC | NE555 timer | 1 |
| 2. | Capacitor | 0.01uF, 10uF | 1, 1 |
| 3. | Variable Resistor | 100KΩ | 1 |
| 4. | Resistor | 330Ω | 1 1 |
NE555 IC Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of NE555 IC
Astable Multivibrator Circuit
Working Explanation
The circuit uses IC 555 along with other passive components to generate the time delays. The On-time and OFF time depends upon the values of resistors and capacitors. The output is obtained at Pin3. The Pin 2 and Pin 6 are coupled together while connected in between the capacitor and a resistor. The capacitor is connected in series with the capacitor connected to Pin 5. The resistor is connected in series with another resistor connected at Pin 7. Pin 4 and 7 are coupled and VCC is applied at Pin 8.
Applications:
- Astable multivibrators are widely used in timing circuits.
- These types of multivibrators are used as wave generators.
- It might be a source of generating higher-order harmonic frequency output due to square wave output characteristics.
- It can also be used to build voltmeter circuits.
- Furthermore, it can also be used as a voltage-frequency converter.
Advantages:
- It is a cost-effective circuit.
- It is simple and easy to build.
- It is power efficient due to continuous switching between the HIGH and LOW states.
