These circuits were found in Exar documentation from the 90s. The circuits use both a small speaker and a piezoelectric transducer. The integrated circuit is not common today.
This circuit was found in a 1989 publication. The operational amplifier supports equivalents. The...
This humidity sensor indicates the different levels of conduction of the sensors through an LED...
Found in documentation from the 70s, this circuit uses components from that time. Some of these...