This circuit uses an unusual operational amplifier nowadays and has a very low consumption. The number in parentheses corresponds to the second channel, for a stereo version.
The circuit shown in the figure consists of a 200mA low voltage drop (LDO) regulator using the...
This circuit was found in an American documentation from the 60's. The transistors are from the...
Found in old documentation, this timer uses a sensitive relay and a 2N2646. The time is given by...