A circuit invented by Grant Richter, and offered by several modular synthesizer manufacturers. The Miniwave can perform several different functions, but it is mostly used as a digital VCO, capable of producing a much wider variety of waveforms than analog VCOs.
The Miniwave contains wavetables stored in read only memory, and takes a phasor control voltage input. When used as a VCO, the user selects a waveform from the memory, and then a sawtooth wave drives the phasor input. At any given moment, the voltage value at the phasor input selects a word from the wavetable, which is converted to a voltage at the Miniwave's output. The sawtooth wave sweeps through the memory from the beginning to the end, causing the stored waveform to be reproduced at the output.
Based on this description, one can see that the Miniwave requires a VCO or some other timing source to drive it. Some Miniwaves contain conventional VCOs which drive the wavetable phasor input, but others require an external source. The advantage to using an external source is that waveforms other than sawtooth can be used to produce different distortions and effects. If a triangle wave is fed to the phasor input, the effect it will have is that the waveform alternately plays back forwards and then backwards. If a sine wave is used, not only will the waveform play forwards and backwards, but also phase modulation of the output waveform will occur, since the sine wave does not increase or decrease at a constant rate.
Other uses of the Miniwave are possible; for instance, using special ROMs that contain staircase waveforms, the Miniwave can act as a quantizer. Some Miniwaves have an input for voltage control of the selected wavetable, as well as bank switching arrangements that allow multiple banks of waveform ROMs to be loaded.