This battery charger circuit was found in the August 1970 issue of Radio Electronics magazine. The circuit uses 4 transistors. Q1 must be provided with a good heat sink.
This National Semiconductor circuit appears elsewhere on this site. The circuit must be powered by...
In this circuit the frequency is determined by the coil and the variable capacitor. Transistors like the...
This circuit is from old American documentation, but the transistor used is still very common...