I am trying to create a circuit that takes a 0.6V-4.8V input, and scales it to a 0V-5V output. I was thinking of using a rail to rail Op Amp, like this one (TLV9041 DCK SC70). I also used a guide put out by TI about designing and system with gain and offset, but when using the calculated resistor values, the output wasn't what I expected. LTSpice has an Opamp called UniversalOpamp2 which I was using to sim.
In the guide I used section 4 which details a system with a positive gain, (m), and negative offset, (b). I set the gain to be equal to 1.2, and the offset to -0.6. Below, I set Rf equal to 100 Ohms, and solved for the other values based on that.
With those values, this is the LTSpice model.
For clarity, the cyan wave represents the DC input of the signal I am trying to shift down. The input will be between 0.6V-4.8V. The green line is the 0.6V I am trying to shift down by. The pink line is the current output, which is just an upwards shift of the V- input.
I believe that since the input V+ signal is always larger than the reference signal, the Opamp will always be active. I can see the the wave of the output, however, I am getting saturated on the upper end and I believe its because the shift is not occurring. I'm sure there will need to be some fine tuning on the gain.
The basic premise of this is that a mechanical mechanism generates a signal that ranges between 0.6V and 4.2V, I want to run this through an ADC converter to send to an FPGA, with a signal between 0V and 5V.
**Original post had the Opamp flipped, updated post reflects the "correct" orientation.