This circuit with the HA2400 was found in the March 1980 Radio Electronics magazine. The circuit has digital-gain control and must be powered by a symmetrical 15 V source.
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...