Bistable Multivibrator with 555 Timer

In the world of electronics, the 555 timer IC (integrated circuit) stands as a ubiquitous component, often considered the workhorse of many electronic projects due to its versatility and ease of use. One of the intriguing applications of this IC is in creating a bistable multivibrator, a fundamental building block in electronic circuits especially digital circuits. Bistable multivibrator can be constructed using transistors and operational amplifier which were explained in bistable multivibrator with transistors and in bistable multivibrator with op-amp.

Understanding the Basics

A bistable multivibrator is a type of circuit that has two stable states, and it remains in either of these states until triggered to switch to the other. It finds applications in various domains, including signal generation, memory devices, and digital systems.

The 555 timer, originally introduced by Hans R. Camenzind in 1972, comprises two comparators, a flip-flop, a discharge transistor, and a resistor network. This versatile IC can be configured in different modes, including astable, monostable, and bistable modes.

Constructing the Bistable Multivibrator

To create a bistable multivibrator using a 555 timer, a few additional components are needed beyond the basic 555 timer circuit. The circuit consists of two resistors, two capacitors, and a few connections to set up the flip-flop configuration. The circuit diagram of bistable multivibrator using 555 timer is shown below.

bistable multivibrator using 555 timer animation
 The key to achieving bistability lies in utilizing the 555 timer's internal flip-flop, which can be triggered by applying an external pulse. By carefully designing the connections and values of resistors and capacitors, the circuit can be made to switch between its two stable states upon receiving specific triggers.

Working Principles

In a bistable multivibrator with a 555 timer, triggering occurs through external means, typically through a push-button switch or other input sources. Once triggered, the circuit switches its output state and remains in that state until another trigger is received.

bistable multivibrator using 555 timer animation

 Upon receiving a trigger, the internal flip-flop changes its state, altering the output voltage levels accordingly. This change in output state is sustained even after the trigger signal is removed, owing to the bistable nature of the circuit. For calculating the component values one can utilize the online 555 Timer calculator.

Applications and Significance

The bistable multivibrator built with a 555 timer finds applications in various fields. It serves as a fundamental component in digital systems, functioning as a memory cell or a basic building block for sequential logic circuits. Moreover, it is employed in signal processing, where its ability to maintain stable states until triggered proves valuable.

Like monostable multivibrator and astable multivibrator(also called square wave generator), bistable multivibrator is used in digital electronics circuits for memory, flip-flops etc.


The utilization of a 555 timer to create a bistable multivibrator highlights the adaptability and versatility of this IC in electronics. By understanding the principles behind its operation and carefully configuring the components, engineers and hobbyists can explore and employ this circuit in diverse applications, contributing to the innovation and development of electronic systems.

Experimenting with different configurations and understanding the intricate working of this circuit opens doors to creativity, allowing enthusiasts to harness its potential in various electronic projects.

The combination of the timeless 555 timer IC and the concept of bistable multivibrators presents an exciting avenue for learning and innovation in the realm of electronics.


[1] Astable Multivibrator with Op-Amp 741

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