I have a 100mV peak sine signal centered at 0. The goal is to input this signal into the Arduino. Therefore I have to amplify the input signal. I am using single rail op-amps so I need to bias my input signal as well.
So far, I have tried to simulate this circuit on multisim. I have attached my circuit diagrams below.
I have succesffully biased the input 100mV sine wave by 1.65V. So my sine wave alternates at 1.65V with an amplitude of 100mV. However, I want to use the full range of arduino ( 0-3.3V ). In the circuit diagram, you can see that I have the non-inverting op amp at the end. But the output from that just gives me a straight line (the white line in the osc.png, green line is the input, red is the output from the buffer).
Can someone explain why this is happening? Or if there is a better solution already for problems like this?
Does multiSim fully emulate op amps? Because a 741 will not work on 3.3V. So just for safety you should choose a different model in the sim. But I think your real problem is that your non-inverting amplifier uses actual ground instead of a virtual ground at VCC/2. The result is that it saturates.
You shouldn't be using 1k resistors for your voltage dividers. Change them to 10 k. Replace your op amp resistors with 10 k as well.
Use this op amp. It was specifically designed for low voltage circuits.
I agree with aarg's comment about the virtual ground. You should only have one voltage divider from the generator. Delete the divider connected to Vcc.
If you know how to calculate voltage divider circuits you can set your generator to any voltage you want and still wind up with a 100 mV p-p signal input to your op amps. Forget about using a 741. For one it is ancient technology from the stone age. Use a modern op amp like the one I linked above.
