The operational amplifier used in this application is uncommon today. This Raytheon circuit can be designed with equivalent operational and the power supply must be symmetrical.
In fact, we can say that this circuit found in documentation from the 90s, consists of an intercom...
The basic integrated circuits of this 1988 multimeter are no longer very common today, but if...
This circuit is from an old publication of the 70's. It can be implemented with modern transistors like the...