Multivibrator

Introduction

A multivibrator is an electronic circuit used to implement a variety of simple two-state systems such as oscillators, timers and flip-flops. It is characterized by two amplifying devices (transistors, electron tubes or other devices) cross-coupled by resistors and capacitors. According to the no of stable states it can be categorized into following three types;

• Monostable multivibrator
• Bistable multivibrator
• Astable multivibrator

Simplest multivibrator circuit consists of two cross coupled transistors and suitable resistors and capacitors are used to define the time periods of the unstable states and various above types can be implemented. This simplest form tends to be inaccurate since many factors affect their timing, so they are rarely used where very high precision is required. Therefore when we need high precision we need to go for digital gate networks or integrated timer circuits.

Multivibrators find applications in a variety of systems where square waves or timed intervals are required. For example sequential logic circuits can be used to build more complex circuits such as counters, shift registers, latches or memories, synchronized circuits etc, but for these types of circuits to operate in a sequential way, they require the addition of a clock pulse or timing signal to cause them to change their state; this clock pulses can be generated by multivibrator circuits.

Monostable Multivibrator

Using BJT

Using NAND gates

Using 555 Timer IC

Bistable Multivibrator

Using BJT

Using NAND gates

Using 555 Timer IC

Astable Multivibrator

Using BJT

Using NAND gates

Using 555 Timer IC