This circuit was found in a 1980s documentation, using a comparator from the time. The configuration can also be implemented with comparators or modern operational.
The circuit below is suggested by National Semiconductor in its 1994 Linear Applications Handbook. The...
This 9 + 9 V symmetrical power supply was obtained in a 1977 symmetric publication but can still be...
This circuit was obtained from a Popular Electronics of the 1990s. The circuit uses a temperature...