Found in Maxim's documentation from the 90's, this circuit uses a component from the time and has its performance curve shown next to the diagram.
Found in an EDN from the 80's, this circuit makes use of an operational one of the time. The...
This circuit can either directly supply a piezoelectric transducer (BZ) or a stage with a...
Only for reference this is a circuito f a commercial receiver of the year 1958. The circuit uses...