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Electronics Engineering

What should be done with the unused inputs of a TTL integrated circuit?


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December 12, 2008 10:13AM

Unused ttl inputs would normally default to logic 1 if left floating. but these inputs could act as antennas under certain conditions and they could pick up noise which can cause the circuit to malfunction. it is better to tie unused inputs to Vcc through a 1k resistor (74LS, 74XX etc) or simply return the inputs to ground. for most other ttl families, the 1k resistor might not be required.- Stan (Nigeria)