How can I attenuate a 0-10V signal to a 0-2.5V output using an OpAMp to feed into an ADC?
In addition to the considerations that Harry has given, you can also take a look at our AD8275, which is a G=0.2 difference amplifier. With a 0-10V input, it will give you a 0-2V output (or you can level-shift the output) so it won't give you the full 0 to 2.5V range.
You can also use something like the dual channel AD8279 or AD8273 and have 2 gain stages at 0.5x each in series to get the 0.25x gain.
There are many ways of doing this, but it depends on a bunch of things.
If you had a perfect voltage source and the ADC was high impedance, you could
use a two resistor divider. If the ADC is low impedance, you could add an op amp
buffer. If the voltage source has some output impedance, then your division ratio
would be off, so maybe you need another buffer on the source. Or you could merge
everything into one stage. But some ADCs require differerential inputs, so now you
need two op amps agaiin, one for the buffer function and one to do an inversion.
But some ADCs require that the differential signal be symetrical about Vsy/2,
so maybe you need an accurate reference. Of course, all of these components, along
with the pc board stray capacitance will limit the frequency response.
If you need seven or eight bits of accuracy over a small temperature range, then maybe
two resistors work. If you need 15-16 bits over a wide temperature range, and your
highest signal frequency is 100 MHz, it's impossible.
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