This circuit can use almost any operating system and has a high input impedance. The power supply must be symmetrical. The circuit was obtained in documentation from the 1980s.
This traditional configuration is from a 1976 publication, showing that nothing has changed since...
This circuit was found in an 80's EDN. The circuit uses a current common CMOS, the 4093 powering...
This circuit was obtained in a1969 magazine. The magazine no longer exists, but the circuit can be...