The CGS575 VCS is an extremely versatile control voltage generator and audio source. In the early 1970s, Serge Tcherepnin developed the Positive Slew and Negative Slew modules for the original Serge synthesizer. In time these merged into the classic Dual Universal Slope Generator. The CGS575 is an adaptation of Serge's original circuit with a few new features.
The VCS is a unity gain voltage follower. The rising and falling slopes are independently and jointly voltage controllable over a wide range.
A detailed analysis, made by Tim Stinchcombe, of the VCS can be found here
VC Transient Envelope Generator A pulse at the trigger input will start the envelope, or a gate input will sustain the level and the envelope will fall when the gate goes low. Rise and fall are independently and jointly voltage controllable, with variable linear and exponential wave shapes.
VC Portamento Voltage is slewed according to the rise and fall times.
VC LFO When the cycle switch is thrown, the trigger input is connected internally to the end trigger output, creating a VC clock with variable waveform and independent rise and fall times.
VC Oscillator While not as wide ranged, or accurate as a dedicated oscillator module, the VCS is still an excellent audio source. The Exp CV input is scaled approximately to the 1V/oct standard. The Output wave can be swept from triangle to saw with linear and non-linear waveforms. End Out also produces a pulse waveform.
VC Non-Linear Audio Processor (Low-Pass Gate) If an audio rate signal is slewed, the module responds like a VCF, and a rough VCA. The signal is low-pass filtered down to silence, similar to a low-pass gate.
Envelope Follower Positive and negative peak detection envelope follower.
VC Pulse Delay Trigger input starts the envelope and a trigger will be produced again at the End Out when the envelope completes its cycle.
Sub-Harmonic Generator If a series of triggers are applied to the VCS faster than the total rise and fall times, the module will divide the incoming signal by a whole number. In the audio range the output will be the sub-harmonic series.