This simple circuit for headphones or small speakers was found in documentation from the 90s. The circuit works with voltages from 5 to 9 V and has good gain.
This circuit is from a 1976 encyclopedia of electrical circuits. The 741 must have a symmetrical power...
We found this circuit in a 1978 publication. The diodes can be 1N4002 or 1N4004 and the secondary of...
We found this ultrasonic emitter in a 1964 publication. The transducer is a piezoelectric type....