The figure shows how to use an operational circuit as a voltage divider. The circuit is from a Radio Electronics magazine from June 1986. The reference voltage is given by a zener diode.
This circuit is used in transceivers, enabling input selection by diode switching through polarity...
This configuration was found in an American publication from the 90s. Operators admit equivalents just...
This circuit was found in an Italian magazine Elettronica Prática of 1977. The transistors can be...