We found this circuit in a documentation from the 90's. Information on the A/D converter was not given but types can be used according to the application.
With this circuit it is possible to obtain an input resistance of 100Gohms for a multimeter, with...
This amplifier, to detect biological signals in implanted transmitters, uses transistors such as...
This application is not modern since few computers have parallel ports. But you can use this...