I'm designing an amplification stage using an MCP6021 op-amp operating from 0 to 5V. I managed to tune the circuit so I get 515.646mV to 4.878 V but I could get like 4.99V if tuned the gain a bit more. The reason for not doing so is because I was suggested to keep a minimum of 50mV from both 0V a 5V due to voltage range limitations of the ADC (I'm using a 10 bit ADC by the way), which would be 4.95V. I've been researching about these "voltage range limitations" but the only limitation I found is resolution, 4.88mV ideally, which is ~10 times smaller than 50mV. Could someone explain what I'm missing? Thanks
The data sheet will provide you the values you need. Your previous question was more general so I suggested 50 mV either side because some ADCs can have zero offset and gain errors that force you significantly inside the "nominal" refernce voltage range.
For the PIC you listed the errors are listed in table 15-12: -
- Resolution 10 bits
- INL +/-1 LSb
- DNL +/-1 LSb
- Offset +/-2 LSb
- Gain +/-1 LSb
So you could have a total of +5 LSb at the zero end of the scale and -5 LSb at the top end of the scale.
5 LSb in a 5 volt signal having 10 bits of resolution is +/-24.4 mV and this would be for ratiometric operation.