This circuit allows you to read resistors up to 20 M ohms, converting it into voltage. The circuit is from the 90s. The operational ones used admit modern equivalents.
The basis of this circuit is a CA3130 operational amplifier. The transistor can be BC548, and the...
This circuit, found in a 73 magazine for radio amateurs, is used in radio localization. The...
This circuit is from an American magazine Popular Electronics of March 1991. The circuit produces both...