This is the main voltage controlled oscillator due to its really beautiful shaped sine wave - it is stable and with the same peak to peak over all frequencies. One can switch between square, triangle and sine wave. In the square/triangle mode one can change with a potentiometer from triangle to sawtooth wave or change the duty cycle of the square wave. In sine wave mode one can shape the sine wave to an interesting “sea saw” wave.
All OpAmps are the rail to rail MCP6002 ICs. For a perfect sine wave one should trim the 500R trim potentiometer to a symmetrically wave.

The oscillation circuit is the same like the PB101 Sync VCO.
The shaping from a triangle wave to a sine wave is made with a similar circuit like it's described in: Lab Activity: Generating sine waves from triangle waves by Analog Devices.


Paper PCB


  • Resistors:
  • 2x 220 Ohm
  • 2x 470 Ohm
  • 2x 910 Ohm
  • 1x 1 kOhm
  • 1x 3.9 kOhm
  • 3x 4.7 kOhm
  • 1x 8.2 kOhm
  • 3x 10 kOhm
  • 4x 51 kOhm
  • 2x 100 kOhm
  • Capacitors:
  • 1x 3.3 nF
  • 1x 100 pF
  • 2x 100 µF
  • Diodes:
  • 1x BAT43
  • Semiconductors
  • 3x BC547 transistor
  • 2x MCP6002 OpAmp
  • Mechanical:
  • 2x IC socket, 8pins
  • 1x pin strip 1×10
  • 1x pin header, female 90° 1×3
  • 1x pin header, female 90° 1×2
  • 1x pin header, male 90° 1×3
  • 1x pin header, male 90° 1×2
  • 3x jumpers
  • 2x mini switch
  • Potentiometers:
  • 1x 500 Ohm Trimmer
  • 1x 10 kOhm
  • 1x 50 kOhm


The PB109 VCO II was designed by Wolfgang Spahn 2017-20.
It is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Creative Commons License