Integrator with bias compensation (CB20991E)

This circuit was found in a Popular Electronics from the 90's. It can be implemented with equivalent operational amplifiers.

High Quality Headphone Amplifier (CB11998E)
This circuit is from an English magazine from 1980, but it can be easily assembled with more...
Pre-stabilization circuit (CB8802E)
Found in Philips' 1968 documentation, this circuit serves as a 6.3 V reference for high stability. |...
Isolation Circuit for RS-232 (CB23588E)
In critical applications of the RS-232 interface, the danger of induced voltages in the cables must...