- Labs project
Low distortion three-phase oscillator
October 4, 2013
This low distortion oscillator uses the three phases of a three-phase circuit, plus the inverse signals to generate an effective six-phase control signal to control the amplitude of the oscillation. This six-phase control circuit requires little additional filtering, enabling a low distortion control signal to be obtained with less than one cycle stabilisation period. It operates effectively from 10Hz to 30kHz, but the bandwidth limitation of the op-amps generates slight distortion at higher frequencies that might be eliminated with a faster op-amp. Performance figures of the prototype circuit show better than -90dB distortion, nothing being visible on a signal anlyser trace at 1Hz and 1kHz, and only a second harmonic at -85dB at 30kHz.
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