Voltage Controlled Quadrature Oscillator
This Voltage Controlled Quadrature Oscillator was orginally designed for the P-4 Analog Console created by Laser Systems Development Corporation in the early 1980's. While the design of the circuit is the same, the layout and components were slightly modernized for use in the Z-5 Analog Console. I have found this design to be one of the most stable and well built quadrature oscillators I've ever worked with, so with permission from the owner of the design, I have been able to make them available individually. The Z-5 uses a total of 7 of these circuits!
  • Board Size: 100mm x 40mm (excludes DB-15HD)
  • Power: +/- 15VDC ~75mA
  • Frequency Rage: 0 - 1KHz (Can likely go much higher, has not been tested though)
  • Output Voltage: ~+/-10V

  1. Hold A - Short both Hold A and both Hold B, this will stop the output and set to a "start" point. Do not short A to B!
  2. +15VDC
  3. Optional LED - Output Impedance 2.2K 
  4. -15VDC
  5. Cosine OUT - Square
  6. FM IN - +15V to -15V input, can be used to frequency modulate the base frequency set by pin 1. 220K input inpedance
  7. Rate IN - +15V to -15V input, sets the frequency of the output, linear response. 100K input impedance
  8. Sine OUT - Sine
  9. Sine OUT - Square
  10. Hold A - See pin 1
  11. Hold B - See pin 1
  12. Ground
  13. Cosine OUT - Sine
  14. Hold B - See pin 1
  15. External Start Point - Used to set a different start point for the oscillator than the one specified by the internal start point potentiometer.
  • Offset 1 - This sets the center point of output pin 8
  • Offset 2 - This sets the center point of output pin 13
  • Start Point - When hold A and B are shorted, this sets the oscillators halt position
  • Symmetry - This sets frequency balance: +15V input=f   -15V input=f (opposite direction)
  • Zero - Sets the window around 0V input for the oscillator to stop. 

It is highly recommended to have an oscilloscope available if you intend on retuning the VCQO!
A word on the Start Point Potentiometer. This potentiometer sets the output of the VCQO when pin 1/10 are shorted and 11/14 are shorted. This is useful in an image rotation circuit.

The frequency range of the oscillator is set by capacitor C2 and C3. These should be as closely matched as possible. I have found polyester capacitors to work very well in this application.
This image shows an original P-4 Voltage Controlled Quadrature Oscillator. Designed by Laser Systems Development Corp., it was the core of the P-4 Analog Console. Just beneath the original VCQO is the newly updated Z-5 control board.