3 phase sinewave generator

I would have assumed that anyone interested in building one of these would have a reasonable understanding of electronics in general and the use of operational amplifiers in particular. This circuit relies on the fact that the phase difference between the output of a Wein oscillator and the junction of the CR in the series feedback is constan
3 phase sinewave generator - schematic

t, regardless of the oscillation frequency. Phases are derived from adding appropriate magnitudes and signs of voltages obtained from these two. It is my version of a circuit I came across in commercially built equipment. The original had a few pre-set pots so one could adjust the amplitudes of and phase differences between the outputs. The pots have been eliminated by using two resistors in series in a couple of places. Due to a bit of lost motion between the shaft and rear section of the dual amplitude-setting pot, there is a very small variation in the amplitudes and phases of the outputs as the direction of rotation is changed. This would have made a total nonsense of using the afore-mentioned pre-sets. It is of no consequence in the application for which it was built, but is a bit disappointing in a pot of this pedigree (Bourns).

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