Looking at the AD7667 datasheet, I have troubles understanding Figure 45. Using the AD7667 in 16-Bit Bipolar and/or Wider Input Ranges.
Why the op amp can convert ±10V to 0-2.5V. Should U2 connect the analog input signal to R2 and R3? But the gain is not right.
If I understand you correctly, you want understand as this circuit convert +/-10 V input range to 0-2.5 V output. You can derive the transfer function of this circuit:
General view: Vout=Vin*k+b, where k is input signal gain, b is constant.
In this case:
If you don't understand how to do it, I can help you.
As result, output range
I hope this help you.
thank you，i understand。
i have another question:
why use the multiplexer (U2)? I thought the R3 connect the input.So the voltage I calculated is wrong.
In fact, to input connect the reference voltage, not R3. U2 provide calibration or autozero mode. In datasheet says about this: "When desired, accurate gain and offset can be calibrated by acquiring a ground and voltage reference using an analog multiplexer (U2), as shown in Figure 45".