This circuit with a CA3018 from RCA at the time was found in the August 1970 issue of Radio Electronics magazine. The current is adjusted by R2. The transistor Q3 in the circuit acts as a zener.

This circuit with a CA3018 from RCA at the time was found in the August 1970 issue of Radio Electronics magazine. The current is adjusted by R2. The transistor Q3 in the circuit acts as a zener.