An analog sawtooth VCO controls pitch by charge current, using 1V/octave exponential scaling

An analog sawtooth is generated by charging a capacitor with a constant current source until it hits a trigger point that discharges it, then repeating. The charge current sets the frequency: more current fills the capacitor faster (higher pitch), less current slower (lower pitch). Because pitch perception is logarithmic, synths use exponential voltage control so a linear control change sounds like a linear pitch change — the 1 volt per octave standard. Much of the circuit design effort goes into implementing this exponential response and cancelling temperature drift so the oscillator stays in tune.

Examples

Doubling the charge current roughly doubles the sawtooth frequency (up one octave). Under 1V/octave, raising the control voltage by 1V raises pitch one octave; by 2V, two octaves.

Assessment

Describe how an analog sawtooth VCO turns a control voltage into a pitch, and explain why the voltage-to-frequency mapping is exponential rather than linear. What does 1V/octave mean concretely?