This circuit is recommended for alarm systems since it has a good output stage. The circuit is from a Radio Electronics magazine from October 1992.
Found in a 1979 documentation, this circuit measures resistances on 5 linear scales. The precision is...
This circuit, from 1990 documentation, can be assembled with BC558 transistors for Q1 and Q2,...
Found in American documentation from the 90's, this JFET stage has an input impedance of 500 M...