| Electronics > Projects, Designs, and Technical Stuff |
| Sensor to ADC - OpAmp design |
| (1/1) |
| raff5184:
Hi, I'm following this tutorial http://www.ti.com/lit/an/slyt173/slyt173.pdf to design an OpAmp to be placed between a sensor and an ADC. On page 4, section "Determining resistor values", it says "Let RG = 27 kΩ". Why? How is it chosen?\ Thank you |
| No.Mad:
Hey raff5184, from my understanding the value 27k is basically put as an example of calculating the rest of resistances and the whole process of adjusting values to those accessible on market. If you compare it to E24 Series, resistor values like 21k, 51k, 270R and so on are widely available from any online shop or Ebay. So simply speaking: it was used as an example for calculations. You could put any value for Rg and calculate the rest as shown. Regards |
| MasterT:
R1 & R2 is a load for Vref. Compromise is to keep R1 R2 as low as possible, since --- Quote ---" RG >> (R1 + R2) then (R1 + R2) and R1||R2 can be neglected" --- End quote --- , and not to overload Vref. Basically, calculation is should be done in reverse, first select R1 R2, than take RG about 100x of R1||R2 (1% tollerance) and last step is calculate RF. |
| Navigation |
| Message Index |