The discussion revolves around the proper handling of unused inputs in a quad 2 input NOR gate integrated circuit (IC). Participants explore whether these unused inputs should be tied to ground or Vcc, considering implications for current draw and output behavior.
Participants express differing views on whether unused inputs should be tied to ground or Vcc, indicating that the discussion remains unresolved with multiple competing perspectives.
There are assumptions regarding the behavior of CMOS inputs and outputs that are not fully explored, including the specific conditions under which current draw may vary.
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 ?