This circuit uses an HA2400 consisting of 4 digitally controlled operational amplifiers. The circuit is from a Radio Electronics magazine from March 1980. The power supply must be symmetrical.
This circuit compensates for the brightness of an LED as a function of temperature. We found it in...
This very sensitive circuit works almost like an electroscope. The FET can be the BF245 and it...
Constant currents from 10 mA to 1 A can supply the load, depending on the selection made by S1. Q1...