SN74LS08D When the input pin is floating and there is no input level, the output pin is high level, and the voltage of the input pin is measured to be 1.3V. What is the cause at this time? How to solve the problem of outputting 0V when there is no input,?
thanks
Open inputs are not guaranteed to have any specific voltage. If you want a specific output, ensure that you have valid inputs.
In the case of LS devices, open inputs indeed behave as if high. You would need to add pull-down resistors of no more than 500 Ω.
It would be a better idea to use a CMOS device like the SN74AHCT08 (which also needs pull-downs, but works fine with 10 kΩ or more).
