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A simple OP Amp Oscillator that always has a steady duty cycle regardless of supply voltage or component values (as long as the ratio of the voltage divider resistors remain the same)
**Please Note:
1. This circuit assumes the power rails of the OP Amp will be the same as the power supply for the circuit. To accurately simulate this in everycircuit , you must make sure to adjust the power rail settings of the op amp to the same voltage level of the power supply any time you change voltage of the power supply….
In the real world this isn’t a concern because the “Vcc” and “GND” pins of the op amp can be (and almost always are) tied directly to the power supply, (as long as you didn’t buy an op amp that specifically requires a split power supply or negative supply rail).
2. To change the frequency, simply alter the values of resistor or capacitor that make up the RC filter.
3. Additionally, the amplitude and frequency of the sawtooth waveform can also be altered by adjusting solely the value of the resistor between the op amps output and non-inverting input. Think of this adjustment as tweaking a threshold offset, where: there is a base threshold voltage that’s set by the voltage divider, and this specific resistor controls the high and low thresholds which are really just an offset level above and below the base threshold, the difference is it’ll be a positive offset for the high threshold but negative for the low threshold.
4. Controlling the duty cycle can be done by adjusting at least 1 of the 2 legs of the voltage divider. For example, if they are equal then the duty cycle will be 50%. You can also calculate the duty cycle by calculating the output voltage of the voltage divider and then the percentage of it reference to the supply voltage, and that should also be the percentage of the duty cycle, or you can use the formula below:
Oscillator Formulas:
Duty Cycle: % = (100*r2) / (r1+r2)
Identifying each component (from the schematic):
R1: 1.01k
R2: 1.02k
R3: 1.03k
R4: 1.04k
C: The Capacitor
Vcc: The Voltage Source
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