Question about CD4051

[AinaLaw]

Hi

I want to know what happen to "not selected" output pin of
CD4051 ? Does it go 3 states ?

If I connect this "not selected" output pin to CMOS INV gate,
what do I get ? 0 or 1.

Thank you

Aina Law

 

[silvio]

A "non-selected" output pin has a high impedance with a typical 100pA residual current (it goes to 3 states )
If this output is tied to an input of CMOS gate, because the input level is not defined you can't count on a 0 or 1 on INV gate output.
You must fit pull-up or pull-down resistor at INV input gate to be sure of 0 or 1 at his output.
This additional resistor will load a little the circuit fitted at pin 3 (common IN/OUT) when the appropiate channel is selected.

 

[AinaLaw]

Thank you for your help.

But can you please give me the formula to calculate the resistor value
for pull up and pull down (if the cmos has +5V).

Thank you.

Aina Law

 

[IanP]

Try this link:
http://www.interfacebus.com/IC_Output_Input_Pullup_Resistor_Values.html

Regards,
IanP