Analog Electronics #8

Questions:

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 the ramp gets, and the bigger the capacitor gets the 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?

Unlike a monophonic synthesizer, which only allows the user to play one note at a time, a polyphonic synthesizer offers more variety by allowing for multiple notes to be played at a time. In order to create a polyphonic synthesizer, instead of having one master potentiometer that connects separately to each of the push buttons and potentiometers, we would get rid of the master potentiometer, and connect each of the notes separately and directly into the comparator. In the monophonic synthesizer, the voltage flows into a master potentiometer which divides into three different signals. However, directly connecting the voltage coming from the comparator into each of the notes would allow more than one to be played at the same time. For example, in order to play 2 notes at the same time, we would connect two buttons and potentiometers directly into the comparator, for 3 notes, we would connect three buttons and potentiometers directly into the comparator, and for 100 notes, we would connect one hundred buttons and potentiometers directly into the voltage, while using the necessary resistors. Theoretically, given that we have enough parts and space, we could create as many notes as we want, and play as many as we want of them at the same time. Overall, removing the master potentiometer and having each push button and potentiometer separately connected to the comparator with their own resistors will allow us to create a polyphonic synthesizer.