Found on 80's Popular Electronics, this circuit uses an uncommon integrated today. Programming is done by a DIP switch.
Found in Radio Electronics from the 90s, this circuit uses a 741 and can be changed to other...
The circuit is of the Motorola Linear Databook of 1990. The power source must be symmetrical and the...
This circuit was found in a 1980s documentation. The operational amplifier is of a common type at the...