This LM380-based circuit was found in documentation from the 1980s. The components are current, and the transistor may be a general-purpose equivalent. Note the use of a medium impedance speaker.
This configuration shows the simple way to use a varicap diode to tune an LC circuit. Capacitor C1 must be...
This circuit consists of a touch switch with optical isolation, using CMOS integrated circuits. The...
Within a range of values, this circuit converts input voltages into corresponding currents. The...