This circuit takes advantage of the noise generated at the reverse biased junction of a germanium diode. Other types of diodes can be used. The signal is weak.
Found in Motorola documentation from the 1980s, this circuit employs an integrated device from...
This input circuit for an oscilloscope was found in Radio Electronics from the 90s. The operating...
This circuit was found in Motorola documentation from 1968, using high power transistors and...