INHIBIT Gate

We’ve previously explored various logical gates within digital electronics, including the basic AND gate, OR gate and NOT gates, as well as others like NAND, NOR, EX-OR, and EX-NOR. With a good grasp of these basics, let’s delve into a special type of gate: the INHIBIT gate. Many times there arise many situations when the logical signals are needed to be either enabled or inhibited which depends upon certain other control inputs. This is where the need of this type of logic gate arises.
The term “INHIBIT” refers to a gate that produces a consistent output regardless of any changes to its inputs. Consider this illustration: a four-input NOR gate with one input permanently set to a logic level ‘1’.
This configuration guarantees a fixed output of ‘0’, regardless of the other inputs, because one input is always ‘1’. So we can say that fixing this one input permanently inhibits the function of the gate. This gate will work like a normal NOR gate only when that input is changed to ‘0’ level. The above illustration explains the INHIBIT function.

This functionality extends to integrated circuit, exemplified by an AND gate where one input is negated by an inverter. The input which is negated acts to inhibit the gate. Or we can say the gate will behave like an AND gate only when the negated input is set at a logic level ‘0’. Now we will see this through the circuit symbol and truth table for a four input INHIBIT gate.

Now in the above diagram if all the inputs of the gate is permanently tied to logic level ‘1’ then the logic ‘0’ at the INHIBIT input will produce a logic ‘1’ at the output and a logic ‘1’ at the inhibit input will result in a logic ‘0’ output. Now we will look at the truth table of the above drawn gate.