In a quad 2 input NOR gate IC, unused inputs should not be left floating to prevent excessive current draw and potential output oscillation. Tying unused inputs to either ground or Vcc is acceptable; however, grounding them can lead to a high output state, while tying to Vcc results in a low output state. The critical factor is ensuring that all CMOS inputs are connected to avoid floating states, which can cause noise and increased current consumption. Properly configured, the IC will draw minimal current when the output is not connected to any load.
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You can tie them either way -- the key is not to let any CMOS inputs float, since they can float to mid-rail, which draws excessive current in the input stage, and can make the output oscillate creating noise. Whether the (open) output pin is high or low doesn't affect the Idd current draw for the CMOS gate.TheRedDevil18 said:I have a quad 2 input NOR gate ic in which I am only using two of the four gates. I have read on the internet that unused inputs must be tied to ground. But if I tie these inputs to ground then I would get a one on the output. Will that draw excessive current ?, should I tie them to Vcc instead so my output is zero ?