Posted on July 18, 2016 at 16:39Hi,
In STM32F373-EVAL board,SDADC is used to measure temperature with PT100 as sensor.The circuit is showed below.
![0690X00000603N7QAI.jpg 0690X00000603N7QAI.jpg](/t5/image/serverpage/image-id/46858i50037963B7493351/image-size/large?v=v2&px=999)
![0690X00000603NvQAI.jpg 0690X00000603NvQAI.jpg](/t5/image/serverpage/image-id/46856i4C33FC4041D0ADC0/image-size/large?v=v2&px=999)
These two pictures are screenshots of tutorials of STM32F373-EVAL board.The document says the gain of op amp A1 is 1.SINCE ''the resistor bridge, R1 and R2, connected to VDD is equivalent to the VDD/2 generator where R1/2 = R internal resistor''.Due to my poor analog circuit experience,I just can not understand this point.
Besides, In the derivation procedure in snapshot 2, the refreence voltage(Vref) is VDD/2(Equation 5).How it get this point?
Best Regards.