This Linear Technology circuit can measure currents from 100 pA to 100 uA. The circuit is from the 80's, using a component of the era. Transistors are general purpose types.
This noise generator uses the thermal noise of a common diode junction. The circuit is from an...
This circuit can monitor the charge and discharge of batteries. The circuit is from a Linear...
This simple electroscope with bipolar transistors is not the most sensitive, but can detect static...