This circuit was found in the Spanish magazine No longer in existence, Mundo Electrónico, in a February 1972 issue. The circuit can still be easily assembled by simply replacing the SC107 with the BC547 and in place of the MC140, the BD135 can be used. This circuit takes advantage of the TR1 base-emitter junction as a reference, keeping the collector off. Input can be from 12 to 16 V.
