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Start the oscillator by slappin' that push button. The output is the ORANGE waveform.
This circuit is a square wave oscillator that utilizes a comparator.
The pot connected to the two diodes controls the duty cycle of the output waveform. Notice how current that charges the capacitor flows through one half of the pot, and current that discharges the cap flows through the other.
The pot connected to the non-inverting input of the op-amp controls the frequency.
Notice how the op-amp is acting as a comparator, and when the blue and green waveforms touch, the output value flips to the other rail.
Play with the capacitance value too and see how it affects the output! The value of the capacitor is basically the way to adjust the frequency offset of the circuit.
Even though this circuit is single supply, the output can be negative. Just AC couple the output by closing the switch right next to the orange voltmeter. The waveform for the AC coupled output is in RED. Notice how this red output is centered around ground, while the orange waveform starts at ground and goes to the positive supply rail.
The N and P channel MOSFETS at the output shield the actual oscillator output from the circuit's output, by providing a high impedance input for the op-amp, and an extremely powerful signal to the output load resistors. Notice its small value of 10 ohms! Woah!
Note: In real life, the frequency response of this circuit ain't too hot. At around the 500kHz range, even with a fast op-amp, parasitics of the passive elements come into play and frequency and duty cycle will be skewed.
Also Note: The duty cycle and frequency potentiometers aren't perfectly isolated! See how one could affect the other at a high frequency!
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