AD623: Low output maximum

Document created by analog-archivist Employee on Feb 23, 2016
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Supply = +5V
Vin+ to 10K to 0v(gnd), same node is output of detector(10k is detector load)
Vin- to gnd, Vref to gnd
Signal is +10mV +/- 300uV
Rg = 100R+500Rpot
22nF cap across Vin+/-
Problem is that output is clipping at about 1.1V. Have tried all I know but
can't seem to change this.
I have used an AD620 with +/- 15V to do this without this problem, but we are
trying to get away from this split rail supply.
What could cause such a low output maximum.? Rload is a 10k resistor to gnd.

 

This is a common problem with single supply in amps. One of the internal
amplifiers saturates even though the inputs and outputs are within the rails.

In the datasheet, figure 22 shows the limitations on output swing vs the common
mode of the input. The solution is to bias up the input away from gnd towards
midscale - this gives the best output range.

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