If you have the skills and can get your hands on SMD components, you can assemble this small amplifier. We found it in the Radio Electronics Experimenter special edition from 1990.
Based on a 555, this 80's American documentation circuit detects the voltage of a battery and can then...
In the figure we have the use of one of the four existing amplifiers in the LM2900 and LM3900 as a...
12 V battery chargers provide higher unregulated voltage. With the regulator shown, obtained from...