Electronic – Non-inverting op-amp with DC offset


I'm trying to amplify an AC wave (from an audio input) with a maximum amplitude of about 1.8v to a DC oscillation between 0V and 5V with the centre (what would be the zero-crossing on the input) at the midpoint of 2.5V.

I've attempted to use a differential amplifier design to achieve this but my output is inverted from the input.

Here's my current schematic from CircuitLab:

And the simulation output:

I'd really like it if I could produce a non-inverted output without any additional active components, how could this be done?

Thanks in advance!

Best Answer

Easiest method:


simulate this circuit – Schematic created using CircuitLab

Component values are left for you to calculate.

Note that the TL081 is NOT an appropriate op-amp, given your desire for a rail-to-rail output swing.

R1 & R2 set the op-amp bias point.

R1, R2, C2 forms a low-pass filter that reduces noise from the power supply

R5 sets the input impedance

R5 & C3 set the input hi=pass filter time constant

R3 & R4 set the gain.

R3 & C1 set the gain-set section hi-pass filter time constant.

Note that if you are not concerned about noise from the power supply line getting into your amplified signal, you can eliminate C2 & R5. In that case, R1 & R2 set the input impedance and R1, R2, C3 set the input hi-pass filter time constant.