This circuit was found in a 90s Electronic Engineering. The quadruple operational amplifier can be replaced by an equivalent. RL determines the tested resistance range.
This circuit is from the 1983 Intersil Databook. In it we have the use of the ICL7135 as an AD...
This MW radio circuit with varicap tuning was found in an English documentation from 1989. The...
This circuit was found in an American publication from the 70s, but it can be assembled with more...