biasfilteroffset
First post so sorry for any bad formatting.
I'm trying to figure out how to bias my signal going through a non-inverting op amp with a gain of 1. Because I want a gain one just 1, it would just be a unity gain buffer with the signal as the input.
1) Lets say the incoming signal is biased at 0V with signal going from -2.5 to 2.5V. How do I bias at 2.5 with signal going from 0 to 5V.
2) How about re-biasing from 2.5V to 1.65V?
Thanks for any input!
You can just use an op-amp adder, or just a voltage divider if you can live with higher output impedance and low input impedance.
For example (voltage divider):
simulate this circuit – Schematic created using CircuitLab
R1 is picked arbitrarily, and the remaining two values are chosen so that R2||R3 = 2.02K (so the output voltage changes 1.00V for a 100V change in the input) and 5V * (R1||R2/(R3+R1||R2) = 1.40V
Output impedance is R1||R2||R3 = 2.0K
Edit: Depending on the accuracy you need (which you did not state) you can use the closest E96 values of 1% resistors (eg. 7.15K, 2.80K) which would give you a gain of 100:0.996 and a bias of 1.393V (nominally). For a higher accuracy divider you could use available 0.1% resistors and combine them with 1% resistors to get very close to the desired values (or simply use something close and adjust the result digitally).
As the output voltage is not at the correct DC level, but the DC bias is correct, change the amplifier. There is lots of other good advide here, particularly @ChrisR decoupling comments. Another point to note is the the virtual earth connections (ive Opamp inputs) are very sensitive to capacative pickup, so ensure that they are routed close to the amp and do not do near potentially noisy signals.
Best Answer
If it's AC, the easiest way is to pass it through a capacitor, then add a high value resistor pulling the signal towards a virtual ground which you would set at 2.5v.
I searched a bit, and it's pretty easy to do with DC as well. You can use this circuit:
Source/explaination here