In Reply to: Re: Switching between analog inputs posted by HEMAL on 01/03/02 at 6:58 AM:
from what I could find about the DG406, its turn on Res=100 ohms, which is high. So I doubt if each of the channels output are the same. Then there is the drive voltage to the gate, is the MUX on hard or what. I also don't know if you are using a constant current source or what. I also don't know if you are using a DC supply or power strobing the circuit during the sample time. Then there is the noise generated by the instrumentation amplifier. Also if you are sampling the 20mv during the settling out time of the MUX. The grounds could also be noisey, crosstalk between channels. Not being there to see your setup is hard without more inputs or some scope readings. Operating down in the mud, so to speak, can be a problem. If you do use a scope watch the loading effect it has on the MUX; ie, the capacitance of the probe, some are very high, so use a FET probe and the grounding scheme.
transition time usec=0.3
typ charge injection(pc)=15