Relaxation oscillators are electronic circuits that generate repetitive waveforms with a characteristic relaxation time. These oscillators are widely used in various applications, including signal generation, timing circuits, and frequency generation. One of the common types of relaxation oscillators is the multivibrator.

Multivibrator:
A multivibrator is a type of relaxation oscillator that consists of two amplifying stages cross-coupled with each other. It is called a multivibrator because it can produce two stable states or oscillate between two states. The two stable states are known as the "high" state and the "low" state.

Working of a Multivibrator:
The multivibrator circuit consists of two amplifying stages, namely the collector-coupled amplifier and the emitter-coupled amplifier. The collector-coupled amplifier drives the base of the emitter-coupled amplifier, and vice versa. The cross-coupling between these stages creates a positive feedback loop, allowing the circuit to oscillate.

When the circuit is initially powered on, one of the transistors is in the "on" state, and the other is in the "off" state. This causes the output of the first stage to be at a low level and the output of the second stage to be at a high level. As a result, the capacitor connected to the output of the second stage begins charging.

As the capacitor charges, its voltage gradually increases, reaching a threshold level. At this point, the second stage switches to the "off" state, and the first stage switches to the "on" state. The capacitor then starts discharging through a resistor, causing its voltage to decrease.

Once the capacitor voltage reaches a lower threshold level, the first stage switches back to the "off" state, and the second stage switches back to the "on" state. This process repeats, causing the circuit to oscillate between the two stable states.

Applications of Multivibrators:
Multivibrators find applications in various electronic systems, including:
- Signal generation and timing circuits
- Frequency division and multiplication
- Pulse-width modulation
- Clock generation in digital systems
- Frequency shift keying (FSK) modulation
- Voltage-controlled oscillators (VCOs)

Conclusion:
Relaxation oscillators, specifically multivibrators, are widely used in electrical engineering due to their ability to generate repetitive waveforms. These oscillators operate by cross-coupling two amplifying stages, creating a positive feedback loop that allows the circuit to oscillate between two stable states. The multivibrator, also known as a relaxation oscillator, finds applications in signal generation, timing circuits, and various other electronic systems.