AD8555: Attenuate and level shift

Document created by analog-archivist Employee on Feb 23, 2016
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I have noticed that the AD8555 amplifier can be programmed to give the desired
gain and offset to a sensor signal. However, the gain values range from 70 to
1280. I need to scale down my signal, so the desired gain should be 0.5. Is
there a similar product that can give me this gain or a way to program an
AD8555 to give a gain of 0.5?

 

The AD8555 is unsuitable for this application.

I would recommend that you use a pair of precision resistive dividers circuit
to divide the differential voltage by 2 - giving you +/-2.5V differential - and
then use a regular instrumentation amplifier like the AD623 to carry out an
accurate differential to single-ended conversion with a gain of 1.

Note that the output headroom of the AD623 can be as much as 1.5V below the
supply, when 1.5mA is drawn from the output. Therefore the AD623 positive
supply should be e:g: +7V and -3V to encompass both the input voltage swing
(+/-2.5V biased around ground) and the output voltage swing (0 to 5V with
respect to ground).

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