Found in an EDN from the 90s, this circuit has a distortion of only 0.003%. Capacitors and double potentiometer determine the frequency.
With this step the motor is energized when the TTL or CMOS input is high. Motors up to 1 amp and...
Other versions exist on this site from various publications. This one is from the Radio...
The load controlled by this circuit depends on the triac used. The circuit is from Electronics Now magazine...