With the oscillator we’re studying the comparator outputs a square wave and the integrator outputs a triangle wave.
With an integrator, if Vin is positive the output voltage ramps down. If Vin is negative the output voltage ramps up.
With a comparator, if the op amp’s + input is connected to a greater voltage that that connected to it’s – input, the op amp’s output will be about positive 9v DC. If the op amp’s + input is connected to a lower voltage that that connected to it’s – input, the op amp’s output will be about negative 9v DC.
The bigger the resistance R you use the slower the ramp gets, and the bigger the capacitor gets the faster the ramp gets.
The circuit at the end of this video is a monophonic synthesizer – it can only output one tone at a time. What do you think you would have to do to make a polyphonic synthesizer that could play 2 notes at the same time? 3 notes? 4 notes? 100 notes?
To allow the synthesizer to play more than one note at a time, you have to use a different resistor for each button.
Emily Dykhouse Analog Lab 