This is my Trapezoid quadrature through zero LFO. Derived from my Trapezoid quadrature through zero VCO. Still using the trapezoid VCO core designed by Don Tillman (used with permission). I found the original article and schematic about the Trapezoid VCO on Don Tillman’s site (Link to original article from 19 July 2003). The article consists off three parts with the core implementation in part 2. I kept the basic idea and changed nearly everything else. I use an other exponentiator scheme and temperature stabilization. Another reference voltage device is used. And quadrature square outputs are implemented. As well as the additional waveforms triangle, sine, ramp up and ramp down. For the LFO I made a few changes. I removed the pulse output and added the missing ramp up and ram down outputs for 180deg and 270deg. Everything else is kept the same as in my Quadrature VCO. This LFO runs from zero Hertz way up in the audio range.

Specs and features

• Runs from zero Hertz to audio range.
• Trapezoid quadrature output
• Square quadrature output
• Triangle quadrature output
• Sine quadrature output
• Ramp up quadrature output
• Ramp down quadrature output
• Through zero modulation
• V/Oct, FM log and trough zero CV input
• Temperature compensated
• Runs on +/-15V and +/-12V
• Power consumption around 110mA each rail

The documentation and the Gerber files for download can be found in my website.