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I've seen a similar question asked earlier here: How do I bias an AC signal for sampling?

However, I have a 3 different circuits and I am not sure which one works best!

I have: +-2V AC signal of varying frequency (5hz to 10kHz). It is biased around 0V.

Objective: Shunt this signal from 0V to 3V, so the output is 1 to 5V signal (the same +-2V just biased around 3V) like demonstrated here:

Desirable outcome

Solution 1: Single Non-inverting Unity gain Op-Amps Here I cheated a little bit by increasing the AC signal from +-2v to +-4V, because the summing amp in this case forms a voltage divider Non-inverting Unity gain Op amp

Simulation: Transient and AC enter image description here

Solution 2: Two Inverting Unity gain Op-Amp in series By adding 2 inverting op amp in series, we can add to signals without "cheating" and scaling the input signals. 2 inverting op amps

Simulation: Transient and AC inverting op amps sim

Solution 3: Three Non-Inverting Unity gain Op-Amps Why? Well, the AC signal source has some impedance, so to avoid any discrepancies on the summing op amp input, I thought it would be logical to put both the AC and DC components through unity gain buffers first... enter image description here

Simulation: Transient and AC enter image description here

All three circuits work and the output signal is in fact 1 to 5V in all three cases. Which solution is the best?

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1 Answer 1

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I would say the first one, though a typically used solution is my schematic below.
The other two are unnecessary complications

All you have to do is use a non-inverting buffer/voltage follower with a DC voltage divider on its input for centering the virtual ground level (of the AC signal) and place a capacitor on its input to separate the DC components between AC signal generator and the buffer input, like this:

schematic

simulate this circuit – Schematic created using CircuitLab

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    \$\begingroup\$ Perfect, thank you so much! I take it as with this approach impedance matching would not be a problem? If for example the V1 impedance is unknown. \$\endgroup\$ Sep 15, 2023 at 10:37
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    \$\begingroup\$ As long as the source impedance (Z_V1 + Z_C1) is reasonably small compared to R3. When the source impedance approaches R3 the AC signal gets attenuated. \$\endgroup\$
    – jusaca
    Sep 15, 2023 at 11:18

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