LM13700 Triangle VCO

The LM13700 OTA chip has an interesting schematic for a triangle VCO in its datasheet. The discreet sawtooth VCO I’m building is too complex for breadboarding and does not deliver a decent sawtooth (probably due to distortion picked up somewhere in the breadboard). Therefor I decided to give the LM13700 triangle VCO a go. The schematic in the datasheet is very clear. All I did was exchange some resistor and capacitor values to ones that I have laying around. I also wanted to achieve a waveform at an audible frequency so I calculated values for a waveform around 500Hz.


The minus input on the second LM13700 has the triangle wave output. The Darlington output on the second LM13700 has the square wave output. The triangle looks like this:


and sounds like this: