This is a small Voltage-Controlled Oscillator - the heart of every analog synthesizer. It provides a square and a triangle wave, and it could be hard synced, too.

The OpAmp is a rail to rail MCP6002 from Microchip.

It is designed to use for experimts and development together with a breadboard.

vc_oscillator_12.zip

• Resistors:
• 1x 1 kOhm
• 2x 10 kOhm
• 1x 12 kOhm
• 6x 47 kOhm
• 1x 100 kOhm
• Capacitors:
• 1x 3.3 nF (foil)
• Electrolytic Capacitors:
• 2x 10 µF
• Semiconductors:
• 1x LED
• 1x OpAmp MCP6002
• 1x BC547 transistor
• Mechanical:
• 1x IC socket, 8 pin
• 2x pin strip 3 pin
• Potentiometers:
• 1x 100 kOhm

Any voltage between 0-5V at the VIN pin can control the frequency. Without any input resistor the potentiometer wont have any effect on the frequency. But with an input resistor and depending on its value both the potentiometer and the input voltage will define the frequency.

 Voltage Source-------10 kOhm-------- Voltage In

For the Sync input one can use any 0-5V source, preferable a pulsed one. A diode in forward-biased direction is needed at the input. An additional resistor can decrease effect of the syncing signal.

 Sync Source -----/\/\/----->|-----Sync Input

If one wants to use the VC Oscillator as a sound source one needs to attach a resistor divider and a 47µF capacitor to the output, depending on outputform it's 470/120 Ohm for the square output and 470/150 Ohm for the triangle output.

                          +  47µF
 square out----470 Ohm-----||-------Line Out
                        |
                      120 Ohm
                        |
                       GND

                            +  47µF
 triangle out----470 Ohm-----||-------Line Out
                         |
                       150 Ohm
                         |
                        GND                      

The Voltage Controlled Oscillator was designed by Wolfgang Spahn 2020.
It is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.