We found this circuit in a 1971 documentation. The circuit can be assembled with more modern transistors such as BC548 for Q1, BC558 for Q2 and BD135 for Q3.
We found this circuit in an old English publication. Transistors are general purpose and the block...
This circuit is from the 80's and can be implemented with modern operational amplifiers equivalent...
This circuit that has excellent linearity using an NTC as a sensor was found in a European...