Found in old documentation, this source uses an integrated circuit from that time, which is uncommon nowadays. The power source has a ripple below 1 mV.
This 1-transistor circuit for currents up to 50 mA was found in the August 1974 Radio Electronics...
This circuit is from 1997 when Camcorder-type video cameras that used powerful batteries were...
This is a commercial circuit for an AM radio with 4 transistors, published in a Japanese magazine in...