This circuit is from an old documentation, making use of an operational of the time. The circuit can be adapted to use modern components. The power supply must be symmetrical.
This interesting circuit, which can be used as an alarm, was found in a 1997 documentation. It...
We found this circuit in the National Semiconductor FET manual. The components are calculated...
The presented circuit is suggested by Texas Instruments (www.ti.com) in its Application Report...