This circuit was found in an old American documentation. It can operate with signals from 40 Hz to 50 Hz and the input voltage range is from 0 to 200 mV.
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...