As a follow-up of the small LFO (see last post), I designed a Printed Circuit Board (PCB) of the LFO, so it is easier to make this circuit for anybody who is interested. Since the LM13700 chip has two OTA’s onboard (2 x Operational Transconductance Amplifier) I also created two LFO’s. (like the design made by Ray Wilson).
One LFO has 3 outputs: rectangle, triangle and sine-wave. With a potentiometer of 50K the frequency can be changed. The switch is added to be able to change the frequency range.
The circuit takes +12V, GND and -12V. It uses the Eurorack standard power-supply connection. Please consider that this is a very basic LFO circuit and notice the amplitudes of the output signal are not constant over the frequency range. But still, a great LFO!
![](http://www.ipson.nl/wp-content/uploads/Projecten/LFO/Circuit_web-1024x707.jpg)
![](http://www.ipson.nl/wp-content/uploads/Projecten/LFO/PCB_values-1024x709.jpg)
![](http://www.ipson.nl/wp-content/uploads/Projecten/LFO/lfo_top_side_web-1024x713.jpg)
![](http://www.ipson.nl/wp-content/uploads/Projecten/LFO/parts_list_web2-1024x713.jpg)
![](http://www.ipson.nl/wp-content/uploads/Projecten/LFO/double_lfo_insouts_v2-1024x893.jpg)