March 23, 2020
Oscillators
1) With the oscillator we’re studying the comparator outputs a square wave and the integrator outputs a triangle wave.
2) With an integrator, if Vin is positive the output voltage ramps down (up/down). If Vin is negative the output voltage ramps up (up/down).
3) 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 (positive/negative) 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 (positive/negative) 9v DC.
4) There’s a formula for how fast the integrator ramps up or down:
change in volts per second at Vout = -Vin / RC
So the bigger the resistance R you use the slower (faster/slower) the ramp gets, and the bigger the capacitor gets the slower (faster/slower) the ramp gets.
5) 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 would have to do to make a polyphonic synthesizer that could play 2 notes at the same time? 3 notes? 4 notes? 100 notes?
You could make two circuits that have the same output. So you have your right hand notes that you could play and your left hand notes. You would be able to play the right hand and left hand at the same time but not different notes at the same time in the same hand.
I don’t know how you would set it up keeping the circuit roughly the same as it is in the video because if you press two of the buttons at the same time, the current going through each potentiometer would be different because they are in parallel causing the tuning to be off.
NYU Electronics 