A Schmitt trigger oscillator is a type of electronic oscillator that uses a Schmitt trigger as its main component to generate a square wave or pulse waveform. Let's break down the components and how it works:
Schmitt Trigger:
A Schmitt trigger is a comparator circuit with hysteresis. It is designed to convert an analog input signal into a digital output signal. The hysteresis feature means that the output switches from one state to another at different threshold levels. This helps to eliminate noise and provide a clean digital signal even in the presence of fluctuations in the input voltage.
Oscillator:
An oscillator is a circuit that generates a repetitive waveform, typically a sinusoidal, square, or pulse waveform, without requiring an external input signal. The Schmitt trigger oscillator generates its own periodic waveform through positive feedback.
Working principle:
The Schmitt trigger oscillator operates as follows:
Feedback Loop:
The Schmitt trigger's output is connected back to its own input through a resistor and a capacitor in a feedback loop. This creates positive feedback, which is essential for oscillation.
Initial State:
Assume the output of the Schmitt trigger is initially in a low state (0) due to the feedback loop configuration.
Charging of Capacitor:
The capacitor in the feedback loop starts to charge through the resistor connected to the Schmitt trigger's output. As the voltage across the capacitor increases, it reaches the high threshold voltage of the Schmitt trigger.
Transition to High State:
When the capacitor's voltage crosses the high threshold level, the Schmitt trigger's output rapidly switches to a high state (1) due to its hysteresis property.
Discharging of Capacitor:
With the Schmitt trigger output now high, the capacitor starts to discharge through the resistor. As the voltage across the capacitor decreases, it eventually reaches the low threshold voltage of the Schmitt trigger.
Transition to Low State:
When the capacitor's voltage crosses the low threshold level, the Schmitt trigger's output switches back to a low state.
Repeat:
The process repeats itself, creating a continuous cycle of the Schmitt trigger's output switching between high and low states. This generates a square wave or pulse waveform at the output of the Schmitt trigger oscillator.
The frequency of the oscillator is determined by the RC time constant of the resistor and capacitor in the feedback loop. By selecting appropriate resistor and capacitor values, the oscillator's frequency can be adjusted to meet the desired application requirements.
Schmitt trigger oscillators find applications in various electronic circuits, such as timing circuits, clock generators, and waveform generators.