This low-noise, low-drift amplifier was found in a 90's EDN. It can be implemented with modern equivalent operational amplifiers. The font must be symmetrical.
SST LLE Series Liquid Level Sensor Switches Available through Mouser Electronics, these solid...
The first circuit is shown in figure 3 and uses a 2N2222 transistor or equivalent. This circuit can...
This circuit shows how an inductive capacitance can be used to reduce the voltage of Power supply...