This circuit can use almost any operating system and has a high input impedance. The power supply must be symmetrical. The circuit was obtained in documentation from the 1980s.
This circuit is from 1995 documentation, with Q1 and Q2 of type 2N2218 or higher power. L1 has 3 + 3...
This circuit was found in a 1965 Radio Shack documentation. The transistors are from that time....
This instrumentation circuit was found in the September 1989 issue of Radio Electronics magazine....