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 electronic switch published in the July 1970 Radio Electronics magazine allows the...
This TTL circuit is from an American publication from 1978, but it can be easily assembled, as...
This circuit was obtained from an English magazine from 1977. The magazine no longer exists, but...