On 9 December 2014 at 03:58, Kardasinski, Milosz <
Milosz.Kardasinski@analog.com> wrote:

> Most PGA's seem to be SPI. Is there any reason you cannot use an I2C
> digital pot in the gain stage of a suitable opamp?
>

The classic 3 op-amp instrumentation amplifier uses a single resistor to
set gain and this can be done across a vast range. This arrangement and
similar is integrated into a single IC in a number of products. So IIC pot
would suffice subject to meeting noise and other requirements.

Here is an expensive and capable dual IA example
A single resistor per emplifier sets the gain.
$US8.66/1 (2 amps). Much cheaper in volume.



http://www.analog.com/static/imported-files/data_sheets/AD8222.pdf




            Russell
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