MFOS Square Wave Oscillator

After the 555 Timer Oscillator experiment, I decided to do some real audio oscillators. This time I was able to breadboard from a circuit diagram and not a video or tutorial. The design I chose was a simple square wave oscillator from the Make: Analog Synthesizers book by Ray Wilson.


This Oscillator requires a bipolar supply with a ground, and, unfortunately, the power supply I decided to buy did not have a ground, it instead has two leads, one for positive voltage, one for negative voltage. I decided to use two batteries connected in such a way that the 0V reference point was between the two batteries (you can see this from one of the images below). It also requires use of an op amp to generate the signal, and I decided to use the TL072.

To get the circuit correct, I decided to look up the datasheet on the TL072, and used the pinouts found there to model the diagram on the breadboard.

My one worry while wiring up the breadboard was that a 9V bipolar supply would not be enough to power this circuit (this was before I was able to calculate the load and power loss of a circuit), but it was a complete success.

As you can see, the oscillations were clean and musical (other than being relatively stuck at high frequencies due to the audio taper potentiometer I had), and the square wave kept its duty cycle all the way up into the high frequencies.

I was able to get the circuit to oscillate between  40Hz and 2.1kHz, which was surprising to me, given that the last oscillator I prototyped had a relatively low frequency range (probably due to my modifications and nothing else).

More than ever I am becoming aware that I need a bipolar power supply and proper potentiometers or trimpots.







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