Actually my original circuit is like i ve 32V to 42V which need be scaled to 0-10V. I used a differential opamp circuit to reduce the voltage to 3.2V-4.2V range.Now i need to change to 0-10V.
I need to use opamp, and in the first stage i had to use differential opamp .so did like that. anythng wrong?or is ther an alternate way?
The voltage gain mus be equal : Au = (10V - 0V) / (4.2V - 3.2V) = 10V/1V = 10[V/V] So gain of a non-inverting amplifier is equal:
Ku = 1 + (R1/R2) then R1/R2 = 9
so R1 = 9*R2 so i start with R2 = 20KΩ R1 = 9 * 20K = 180KΩ.
And we wont for Vin = 3.2V Vout = 0V and this can only be done when non-invent input "+"V is equal inventing input voltage "-"V.
So we have this situation:
So voltage divider voltage must be larger then 3.2V by voltage drop on a R2.