A relaxation oscillator is an electronic circuit that generates a periodic waveform (usually a repetitive signal) without the need for an external input or clock signal. Instead, it relies on the charging and discharging of a capacitor through a feedback loop to create a cyclic output.
The key component in a relaxation oscillator is a non-linear device, often a transistor or an operational amplifier, along with passive components like resistors and capacitors. The circuit operates by charging a capacitor over time and then rapidly discharging it, leading to a repetitive cycle of charge and discharge.
Here's a generalized explanation of how a relaxation oscillator works:
Charging Phase: Initially, the capacitor is discharged and begins to charge slowly through a resistor connected to a voltage source. This charging process continues until the voltage across the capacitor reaches a certain threshold level.
Discharge Phase: Once the capacitor voltage reaches the threshold, the non-linear device switches its state, causing the capacitor to discharge rapidly. The capacitor voltage drops significantly during this phase.
Repeat Cycle: After the capacitor discharges, the non-linear device switches back to its original state, and the charging phase begins again. This cycle then repeats indefinitely, producing a periodic waveform.
The time it takes for the capacitor to charge and discharge determines the frequency of the oscillator's output waveform. By adjusting the values of the passive components (resistors and capacitors) and the characteristics of the non-linear device, the frequency of the output signal can be controlled.
Relaxation oscillators are used in various applications, including generating clock signals for digital circuits, as audio oscillators, in radio frequency (RF) circuits, and as pulse generators in various electronic systems. They are relatively simple and widely used due to their ease of implementation and versatility.