This sensor circuit for currents of the order of nanoamperes was found in an American documentation from the 1980s. The components are from that time.
Suggested by a 1966 publication, this circuit applies a 60 Hz signal to a transistor to test its...
This circuit is indicated to operation with piezoeletric transdicers or other with high impedance...
Two operational amplifiers are used in this source obtained in an American documentation...