This amplifier for electrometer can work with currents of 0.1 pA in a band of 1 Hz. The circuit is from NASA in a publication of the 60s. Transistors are general purpose types.
Found in a 1990s US publication, this alarm circuit detects when a light beam is interrupted. Optical...
This circuit for a commercial compact digital multimeter was found in the March 1979 issue of...
The flasher we present was found in a 1982 publication, shown in the figure. What we have is a...