OK to tie several inputs together? CD4051 chip

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Merlysys

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We often connect same point of a circuit under test to several instruments if the instruments' input impedance is in the megahoms range. Is it OK to do same with several CD4051BE inputs? Meaning there are several 4051s (say 3) and the same point of circuit need connecting to those 3 chips. How to determine this using the datasheet? Or is it common knowledge based on the IC family?

Inputs referred to are marked in red, CHANNEL IN/OUT.
Datasheet at **broken link removed**
 

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Yes, it's perfectly OK to do that in all but extremely critical applications, ones where the input capacitance of the pins might cause timing problems. That would be very unusual though.

Brian.
 

Its the driving device that might have the problem. ICs have a parameter called " fan out", for the TTL series, the outputs can deliver 10 mA, but each input needs 1 mA, so you can connect one output to ten inputs. Connecting 20 inputs to one output will not work. With the 4000 series chips its different as the inputs consume micro amps, but the outputs can still deliver 10 milliamps, so the fan out is enormous, certainly beyond what any one would need. But as Betwixt said each additional input has a small capacitance associated with it, so every extra input will delay the signal slightly.
Frank
 

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