This amplifier was found in a 1969 Mullard documentation. The circuit uses transistors that have as modern equivalents the BC548 and BC549.
The circuit with a common operational amplifier uses a zener as a reference. The circuit is from...
This circuit was found in a 90’s Popular Electronics. The circuit is used to analyze noise in...
This 1989 circuit activates a protection relay if one or two phases are missing from a three-phase...