ls74xx inpedance pin in.

What is the impedance of the input pin for a ls74xx? I can't find it.I found a datasheet but it's seems too low. If it's right and the pin impedence is too low, is necessary a pull-up resistor?


I have no idea what chip you are talking about. Give a full part number or series.

You don't believe the datasheet? Then how can we dispute what the manufacturer says?

If you want more help, give all information on the part and a link to the datasheet. Then tell us what you don't believe with a reference to the datasheet.


What is your reason for asking?

ttl inputs tend to "float" high but its a poor practice to leave floating inputs, either drive them properly or use pullups

If it's right and the pin impedence is too low,

Too low for what?

A 74LS07 has typical input impedance, it takes a current of 20uA at 2.4V for a logic one. That is an impedance of 120K and a current of -0.2mA at a voltage of 0.4V for a logic zero. Note you have to sink current from the input to make it a zero.