The converter based on a Type CA3080 operational trans-conductance amplifier (OTA) converts a triangular voltage into a sinusoidal one with very low distortion. An OTA is a device whose amplification can be varied by a control current.
The circuit needs a stable, precisely symmetrical supply voltage, since the control is derived directly from this via resistor R2. It also needs a symmetrical triangular voltage at a level of 350 mV p-p at pin 3 of IC1. The output in those conditions is a sinusoidal voltage at a level of 2.85 V r.m.s. Provided the circuit is constructed carefully and P1 is set correctly, the distortion does not exceed 1.2%. The figure deteriorates rapidly when the supply voltage is not accurate or precisely symmetrical.