The circuit is from 1980s Linear Technology documentation. The components are of the time and circuit behavior curve is given along the diagram.
May 2017 - Panasonic's new APS1 series of optical couplers with 3 750 V insulation and up to 50...
The operational ones used in this circuit are not common today, but the circuit can be implemented with...
The operational amplifier used in this circuit from a 1970s publication is no longer easily found...