We found this circuit in the Linear Applications Handbook of the National Semiconductor of 1994. The circuit can be adapted to use other operational amplifiers and the power supply must be symmetrical.
This simple alarm was found in a 1982 documentation, but uses components that are still common,...
Found in a 1969’s Electronic Design, this circuit operates in a narrow range of voltages....
This experimental circuit was found in a technical publication from 1976. The diode can be of...