This signal conditioner humidity sensor was found in a 1980s Linear Technology documentation. The circuit uses components from the era that can be designed with modern equivalents.
This circuit, obtained from the component manual used, has an ultra narrow 1 kHz range given by...
Mouser Electronics is providing the MGA-622P8 low noise amplifier for frequencies from 1.5 to 2.7...
This circuit of the 1970s uses Germanium transistors. Changes can be made to use silicon...