input side the basic circuit is comprised of resistor 15 and transistors 17 and 18 additional inputs indicating by shadowed transistor 21 at input c can be provided by adding additional transistors in parallel with transistors 17 and 18 resistor 16 and transistor 19 provide a path for current to flow when both inputs a and b all inputs are inhibited the sources of all the transistors 17 19 and 21 are tied together and connected to a constant current source 20 in the schematic the power supply voltages are shown as v dd and v ss in this circuit v dd may be quite small for example 1 8 volts or less while the input voltage swings will typically range from 400 to 800 mvolts v ss is commonly operated at ground potential the current paths in the circuit are clearly seen to be through a resistor 15 transistor 17 and current source 20 and or b resistor 15 transistor 18 and current source 20 or c resistor 16 transistor 19 and current source 20 again resistor 16 and transistor 19 provide a path for current to flow when both input signals a and b are low 0 state at the very center of this invention is the way the gate of transistor 19 is controlled.