Electronic – Adding offset voltage to sensor signal

offsetunity-gain

I have a pressure transducer outputting 0-5V which is sampled by an ADC with a 0.5V minimum input voltage. I need to offset the sensor output voltage by a fixed voltage of 0.5V. I've looked at an op amp circuit for doing this. But I struggle with finding a practical way of generating a reference offset voltage that is temperature stable (I'm not sure about using a resistor divider down from Vdd).

Any ideas would be appreciated.

Incidentally, the upper limit of the ADC is irrelevant, as we will never get an output signal in that range. Therefore, I want unity gain.

LTspice circuit
Simulation result

Best Answer

My first reaction is to get a better A/D converter. There are many many out there that can directly convert from the 0 to 5 V range.

You didn't say what the upper end of the A/D range is, but if it's 5 V, then you don't want to add a offset, but rather scale the signal towards 5 V. Put another way, you want to map 0 to 5 V --> 500 mV to 5 V. That's not adding a offset.

Fortunately, scaling relative to 5 V is easier than adding a offset. All you need is two resistors:

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