This circuit is an oscillator that generates a sawtooth wave. It's basically the same circuit as the triangle wave oscillator, except that the resistor in series with the capacitor has been replaced by two resistors, each paired with a diode going in opposite directions. For the first half of the cycle, the capacitor charges through a 40k resistor, and for the other half, it quickly discharges through a 5k resistor.
To hear the waveform, increase the simulation speed and press the Play button.
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