This circuit can detect static charges or extremely low voltages. The circuit was found in ancient American documentation and makes use of a JFET. A BF245 which is a more modern transistor can be used.
This circuit that can amplify signals from 0 to 30 MHz was found in a 90s Popular Electronics....
August 2017 - STMicroelectronics' BlueCoin development environment is available at Mouser...
In this circuit the output current is limited by R3. For a 300 mA current, R3 must have 12 Ω. For...