Astable Multivibrator with E-MOSFET

Astable multivibrators are fundamental in electronics, serving as key building blocks in various applications like timing circuits, waveform generation, and oscillators. When combined with E-MOSFETs (Enhancement-Mode Metal-Oxide-Semiconductor Field-Effect Transistors), these circuits exhibit unique characteristics and advantages. There are different types of oscillators, astable multivibrator classified as relaxation oscillator, generates square wave which are used for clocking signal in digital electronics circuit and for PWM signal generation. Astable multivibrator using op-amp and astable multivibrator using 555 timer was also explained in earlier blog post. In this blog post, we dive into the world of astable multivibrators powered by E-MOSFETs to understand their working principles, applications, and advantages. Here IRF540N N-channel enhancement MOSFET.

Understanding Astable Multivibrators:

Astable multivibrators, also known as oscillators, are free-running multivibrator circuits that generate continuous square or rectangular waveforms without the need for an external trigger unlike monostable multivibrator and bistable multivibrator. They switch continuously between two unstable states (high and low) generating a square wave output.

E-MOSFET Basics:

E-MOSFETs are a type of field-effect transistor characterized by their ability to amplify and switch electronic signals. They consist of three terminals: gate, drain, and source. In enhancement mode, these transistors are normally off and require a positive voltage at the gate to turn them on. Here we will be using IRF540N n-channel MOSFET which is not only used for construction of astable oscillator but also MOSFET based amplifiers.

Astable Multivibrator Circuit with E-MOSFET:


  • E-MOSFETs IRF540N (usually a pair)
  • Resistors
  • Capacitors
  • Battery(3 to 9V)
  • Lamps or LEDs
  • Wires

Working Principle:

  1. Initialization: Initially, one E-MOSFET is conducting while the other is off.
  2. State Change: Capacitors charge and discharge through resistors, leading to a continuous switching between the conducting and non-conducting states of the E-MOSFETs.
  3. Output Waveform: The output generates a square wave with equal high and low durations.

Circuit Diagram of astable multivibrator using MOSFET is shown below.

astable multivibrator using MOSFET animation

 The operation of astable multivibrator with E-MOSFET is exactly the same as the operation explained in astable multivibrator using transistor.

Advantages of Astable Multivibrators with E-MOSFETs:

High Efficiency:

E-MOSFETs offer low on-resistance and high switching speeds, leading to improved efficiency compared to other transistor types.

Precise Timing:

These circuits provide precise and stable square wave output frequencies, making them ideal for applications requiring accurate timing.

Ease of Implementation:

The use of E-MOSFETs simplifies the design and enhances the reliability of astable multivibrators due to their robustness and low susceptibility to temperature variations.


Signal Generation:

Astable multivibrators with E-MOSFETs are commonly used in signal generators, where a stable square wave output is required.

Pulse Width Modulation (PWM):

They find application in PWM circuits for controlling power delivery in systems like motor speed control, lighting systems, and voltage regulation.

Clock Generation:

These circuits serve as clock generators in digital systems, providing precise timing signals for synchronous operations.

See video demonstration of how astable multivibrator with MOSFET works.


Astable multivibrators utilizing E-MOSFETs offer a robust and efficient solution for generating square waveforms in various electronic applications. Their ability to provide stable timing signals, high efficiency, and ease of implementation makes them indispensable in modern electronics. Engineers and hobbyists alike can leverage these circuits for precise timing, signal generation, and control in a multitude of electronic designs.

By understanding the principles and advantages of astable multivibrators with E-MOSFETs, innovators can harness their potential to create more efficient and reliable electronic systems across diverse industries.

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