This circuit was found in the Linear Applications Handbook of the National Semiconductor of 1994. Some of the components used are not easy to obtain, but equivalents can be used.
This circuit is from a Radio Electronics from October 1963. The LDR and transistors are from the...
The figure shows how to use an operational circuit as a voltage divider. The circuit is from a...
This is the basic configuration of an operational amplifier as a current regulator. We found it in...