Found in a 1980s documentation, this amplifier uses an integrated circuit that is not easy to obtain now as it is of the era. The circuit is intended for FI ceramic filter circuits.
The circuit presented emulates an OR gate with the LM3900, operational transconductance amplifier....
This circuit was obtained from a 1962 magazine. It can still be mounted to be powered from 6 V...
The figure shows how to implement a conventional current monitor with differential amplifier on an H...