We found this circuit in the May 1989 Radio Electronics magazine. The circuit can have its values changed to operate at other frequencies and the power supply must be symmetrical.
In the circuit shown in the figure we have the way to excite a small speaker from a TTL output. The...
This simple circuit is from a Radio Electronics from August 1952. The current depends on the...
Found in an Electronic Design, this small power source uses a battery as a voltage reference,...