want to convert an output of one of the module whose full Scale Range is 0.4 to 3.6V ... this needs to be scalled to FSR 0 to 3.3V ... when corellated this gives a linear equation Vout = 1.03125 * Vin - 0.4125, i can use the VCC to be between 4 to 5V, how can this be implemented using Opamps. with an error budget of 20mV max
Rgds,
Manju

 

You can use a non-inverting amplifier with gain of 1.03125, then a subtractor (differential amp with gain of 1) with 0.4125V. I'm not sure how you can achieve only 20mV of error fullscale, over temperature, with gain errors, etc.

http://en.wikipedia.org/wiki/Operational_amplifier_applications#Differential_amplifier

Steve

 

If you want to minimize the offset errors then you have to use precision op-amps. They are designed to have low offset voltages. Also, for better results use resistors with an accuracy of 1% or less.

 

Using 1% isn't even going to help him.. His total 'error budget' is 20mV. Due to gain error alone, assuming about a gain of 1, he can be off my 2% not assuming anything else. (2 resistors, each going away from eachother), 2% of about 3V is 60mV.

He needs 0.1-0.2% resistors with good tempco if he wants accuracy over range. This is just one factor for a circuit like this.

Steve