One can imagine a lot of op amps with tri-state output circuits, and a summing junction... but the feedback gets in the way.
A mux/amplifier combination (like PGA116 from TI) at least has a 'typical' graph of the crosstalk...
Is there any point in looking into optoisolators with MOS outputs as switches? It's slow to switch, but an open channel has good bandwidth. TLP172 claims under 1 pf OFF feedthrough capacitance.
signals.
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Whoosh. Look at the data sheet again. Which figure is the crosstalk test configuration?
?-)
I have a different definition of "crosstalk." I don't want unselected channels leaking out of my test connector.
test
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Then you should not expect any better than 50 dB isolation.
?-)
4066 seems to be able to do what your after t-switch etc, but it is not in anyway an elegant solution. Just grounding the unselected inputs is easier but your still looking at 3 chips (my boe figure
If one is going to bother making a built-up T switch, one could replace the shunt branch with a diode. Lower capacitance, lower ON resistance, two per package, cheap, won't load down the input.
Cheers
Phil Hobbs
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