In the figure we have one of the many ways to program the counting of a 4017. The circuit uses additional gates and was found in the Radio Electronics magazine of April 1989.
This amplifier from 100 to 150mW was found in a Japanese documentation from 1967. The circuit uses...
This circuit is from a manual of JFETs and can be implemented with the BF245 and for the bipolar...
This source of some amps for voltages up to 40 V was found in an Italian magazine Elettronica...