With this circuit, from an old operational datasheet, it is possible to measure the CMRR, rejection in common mode of an operational one. The power supply must be symmetrical.
This circuit was found in a 1975 documentation. Current general-purpose transistors can be used,...
We found this circuit in a publication for radio amateurs in 1974. The bipolar transistors can be...
This conventional humidity or water alarm circuit was found in an English documentation from 1974....