This circuit found in an American documentation from 1964, alters the duration of a pulse and can operate at frequencies up to 10 MHz. The transistors 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...