74ls08 giving output without inputs

Thread Starter


Joined Apr 11, 2016
Hello everyone,

This is my first electronics project.
I am using 74ls08 AND logic gate, The Vcc is 4.5 V with no resistors, Now when I'm giving two inputs at pins 1 and 2, I get True(1) at the pin 3. When I remove any of my input, I still get True output. If I'm removing both of my inputs even then the result is coming out to be true. I don't understand what is happening with the Gate IC.


Joined Oct 2, 2009
How do you know what is the logic input when nothing is connected?
Is it 0 or is it 1?

Better to make sure.

For 0 input, connect it to GND.
For 1 input, connect it to Vcc.

No connection means the input is floating.


Joined Mar 14, 2008
With CMOS logic an open input is indeterminate, it could be a 1 or 0 or in-between.

With bipolar TTL logic you have to sink current for a logic 0.
An open TTL input normally goes to a logic 1.