Matching Analog output to ADC's Input

[Sobakava]

I'm trying to get samples from output of a sensor.

Output varies between 1.1V to 3.8V.

My ADC (it's a 16bit ADC sampling at ~80Ksps ) has only positive external reference (VREF) input.
I used an external tempereature compensated precision 4.096V voltage reference.

Now it is sampling 0 to 4.096V . But my signal is only at 1.1 to 3.8V . So I'm loosing from resolution.

I decided shift my signal around 1 volt by using an opamp and replacing 4.096 reference by a 3V reference... But I need to generate very precise and temperature compensated -1V for the opamp.

Any ideas for my problem? Another 16bit ADC with both negative and positive reference inputs or shifting signal to the ADCs's input?


Best Regards
sobakava

 

[tekno1]

ADC input and internal sampling structure is important. I will try to use adifferential input ADC and Vin- will be set to min 1.1V and Vin+ max wil be 3.8V. If ADC input sampling is capacitive and ADC has diffrential input this may work. Sampled Vin value will be (3.8-1.1)=2.7V and using 3V reference will be close (or gain up 3.8 V and 1.1V to make the difference 3V exactly).

One issue is of course, to make sure 1.1V min is exactly what sensor provides, otherwise one has offsett error.

Hope this will set you in right direction.