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.
This circuit provides a symmetrical voltage of 15 V output from the 6.3 V secondary of a small...
We found this circuit in an American 1980s documentation. The operational ones used are not common...
This transistor source can supply currents up to 2 A and the voltage determined by the zener...