[SOLVED] open circuit Input 74hc04 What will be the output?

[azadfalah]

Hello friends

If the input 74HC04 is open circuit , What will be the output?

vcc = 3.3

 

[std_match]

The input is "floating" and act as a capacitor with low leakage. It is impossible to say if it will be high or low.
For the older 7404 and 74LS04 families, an unconnected input is high, so the output would be low.

 

[Audioguru]

An open 74HC very high input impedance input might easily be destroyed by static electricity or it might pickup radio or mains signals. If the input voltage floats at near half the supply voltage then the output will be linear conducting a fairly high current that will overheat and destroy the IC.

 

[crutschow]

In summary never leave any unused inputs on any CMOS circuits floating.
They must all be tied high or low, as appropriate for the pin function.

 

[hobbyckts]

If the input 74HC04 is open circuit , What will be the output?

Why you want to leave it as unconnected?

 

[azadfalah]

This problem was solved i should use pull up resistor

74hc04 input from 74hc573 and if i disable 74hc573 using OE pin this can make high impedance input for 74hc04

Thanks to all friends