Using the LM170 integrated circuit, this circuit was found in the May 1970 Radio Electronics magazine. The transistor is general-purpose, and the potentiometer adjusts the gain.
The figure shows three circuits for using headphones in amplifiers with speakers that do not have...
In this charger, the charging current is basically limited by the LEDs. The transformer is a low...
This configuration is from an old integrated circuit manual. The circuit can be applied to modern...