The main feature of this circuit found in an old American publication is that it is powered by the very signal it converts. The transistors are of the time and can be replaced by current types.
The voltage gain of this DC amplifier is 100 times, given by the relationship between R2 and R1....
We found this circuit with an operational transconductance amplifier in the Motorola Linear...
This circuit, shown in the figure, consists of a variable gain amplifier with differential input...