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Re: AD8221 Problem

Question asked by hallehe on Apr 18, 2012
Latest reply on Apr 20, 2012 by ScottH
Branched from an earlier discussion

Hi Matt, ^_^~


I also want to ask questions about AD8221 here. Actually I built a very simple circuit with it, just as Figure 47 in AD8221 Datasheet (rev.C). I use 500ohm as Rg, +-15V as Power Supply, with 0.1uF capacitor on each power supply pin to REF, REF is connected to ground, load is 10kohm. I just wanted to test this circuit but encountered problems.


My input is generated by a TEKRONIX Signal Generator, and its negative polar is connected to ground. Input range is 10mV to 100mV, f is DC to 1kHz. But no matter which signal I tried, the output stayed on zero all the time! No Output...By the way, I use non-isolation oscilliscope to observe the curve, so -IN and REF can be viewed as tied together. I really don't know the I need some special measure instruments, like isolation probe, to observe circuits with AD8221 ?


Another question is, must the REF to be tied with the middle point of the Power Supply (I mean the 0V point) ? If not, what is the range of their difference? REF can be maximum as +Vs and Minimum as -Vs ?


Hope you can help me with that.


- Halle