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How to sample negative voltages in msp430fg4618?

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Back to reality.


The operational amplifier is not working above its power rails. To use an operational amplifier for processing negative input voltage - it is necessary to use a negative supply voltage.


There is another way to handling the negative input voltage:

1) allow buffered output reference voltage at the output pin.

2) use a voltage divider (two resistors) - one end of the reference voltage, the other end to the negative input voltage and the center of the analog input.

3) select resistors so that the analog input voltage was always greater than zero.

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I agree. There is no way to do this with a single supply op amp. With a dual supply (+/-) then yes you can do it.


Another way to do it is to use a bridge rectifier. Yes, you will have a diode drop in the way but it will make every signal be above ground.


How accurate do you have to be?

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