This circuit is designed to measure very weak currents, in the order of picoamperes. We found it in an American documentation from the 80s. The integrated circuit is from that time.
This circuit is from a 1975 Motorola manual. The FET can be the BF245 and the output voltage...
We found this circuit in a 1980 documentation. With basic changes, including transistors that were...
This circuit not only indicates when the battery is on but also when it is low. The circuit is...