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I'm kind of new to this and hope someone with more experience can give recommendation or even a schematic suggestion.

I have one function generator (Agilent) and one DC source (Agilent). The signal generator is set to send out a signal of 180KHz with Vpp5V, I don't want the signal to go below zero so I add DC with a Bias-Tee and "lift" the AC signal by adding let say 10V DC, so now AC is turning around 10V (5V<->15V). This I can do and it works well. What I want to do now is to divide the output from same setup in three output signals, with the difference of DC level but with the same AC level. For example I want to set the input signal to AC5V DC10V and on the output get: Output1= AC5V DC12V, Output2= AC5V DC14V, Output3= AC5V DC16V. It can also be that the input signal is AC5V DC20V put with the demand of output as above.

I understand one solution is to have three different DC power supply with three different Bias-tee, but if it can be solved in a easier way I would prefer that.

Than you for your help

AKE
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  • This is unrelated, but: Depending on the model of your function generator, you may be able to put a DC offset on it just by changing its settings. You don't necessarily need any external circuitry, unless it's a very cheap or very old function generator. – Hearth Mar 27 '20 at 15:51

2 Answers2

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It depends what load needs to be driven, and what you think is 'easy'. One solution, making some assumptions about both (which if false invalidate the answer) would be the following

schematic

simulate this circuit – Schematic created using CircuitLab

Adjust the pots to get your desired output voltages, or replace them with a fixed pair of resistors for fixed voltages. Of course if to need to drive any significant output current, you'll need to add buffers. This is where 'easy' might mean three power supplies, rather than one supply and some active electronics.

Neil_UK
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  • from where the output has to be taken ? – Sadat Rafi Mar 27 '20 at 11:46
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    @SadatRafi There's a scene in the Matrix (don't know which one) where Morpheus says 'I see three ships, three captains, three objectives. I see destiny!'. The OP asked for three outputs. Do you see three lines leading off anywhere that might ... have ... something to do with ... your question? – Neil_UK Mar 27 '20 at 12:07
  • :v :v :v .. You can be a great poet – Sadat Rafi Mar 27 '20 at 12:47
  • Your circuit seems very efficient to me. I can't test it right now for the corona outbreak. :( – Sadat Rafi Mar 27 '20 at 12:50
  • Thank you Neil_UK, this is a great suggestion and very easy to evaluate. I will just need to order some pots and will be able to try it out. Thank you so much. – AKE Mar 27 '20 at 13:17
  • I've drawn it as pots, but you can use pairs of fixed resistors if you don't need it adjustable, or to try out without needing to buy pots. – Neil_UK Mar 27 '20 at 13:23
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You can do it easily using a differential amplifier. And for any kind of amplification, adding or substructing ap amp is the best to use. I've provided a schematic and simulation results.

Schematic

Simulation Results: Simulation results: enter image description here

The op-amps on the left side are used as an input buffer. The potentiometer will generate the voltage level that you want to subtract. And the op-amp at the right sight is the differential amplifier. If you don't use the buffers, your output will be wrong.

You will find enough resources on youtube about how a differential amplifier works. Thanks.

Sadat Rafi
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    Thank you Sadat for your suggestion, I think it is a very good option but it requires more DC sources for running the Op-amps which I at this stage don't have. But I will review the option if other suggestions does not work. – AKE Mar 27 '20 at 13:17