This circuit was found in a 1967 Electronics World. We can design it with a BF245 for the FET and a BC558 for the bipolar transistor. The circuit has 3 scales and a 10 M ohm input resistance.
This circuit was obtained in an American documentation translated in the 80's. The circuit can be...
This circuit is from a 1998 Electronics Now and can be easily assembled since it uses a common...
This circuit was suggested by National Semiconductor in its Linear Application Handbook. The...