This circuit has a correction or linearity adjustment. We found it in Ferranti's transistor manual from 1974. Transistors are general-purpose types at the time.
We found this circuit in an American documentation from the 60's. The transistors are made of...
This circuit is from the documentation of the 90s. The integrated circuits are from that time. The...
We found this circuit in a 1967 Japanese technical magazine. The transistors are made of germanium at...