The low-noise amplifier shown uses a rare Raytheon operational amplifier today. The circuit can be implemented with more modern operators and the power source must be symmetrical.
This circuit, suggested by Signetics can be used as a shield. Modern operational can be employed...
In the figure we have a typical voltage follower. In a voltage follower the voltage gain is...
This 2001 circuit uses common transistors and can be used in an electronic lock. The relay trips...