This circuit using only transistors was obtained from Ferranti's 1969 documentation. It can be made from modern transistors. The circuit is 4 bits.
Found in a 90's EDN this circuit can be used as a shield. The transistor is a general-purpose type and the...
This circuit was found in the November 1992 issue of Radio Electronics magazine. The circuit has...
This circuit was found in an American documentation from 1977. The circuit can be implemented with modern...