[sdiy] Limiting current through 74-series 4051

[Mark Rivera]

Hi all,

I need to limit the current going through the switches of a 74-series
4051 (0V Gnd/Vee, 5V Vcc). I am using the 4051 as a demux.. 8 DC
inputs to one output. The output is feeding into a single-supply,
rail-to-rail (0-5V) opamp with voltage-follower configuration.

The input sources (pots as voltage dividers) can be anywhere between
Gnd and Vcc.


Is there any difference between these two setups:

1. voltage sources -> 8 resistors -> inputs -> output -> opamp in+

2. voltage sources -> inputs -> output -> 1 resistor -> opamp in+


Theoretically, I think there's not, but I wonder about having lots of
current available at the inputs versus having restricted current at
the inputs. Does it affect the lifetime or performance of the 4051?

(Ultimately, opamp output goes into an ADC.)


Thanks,
Mark