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Simple question of this project:

Is filtering useful here, and if so how to choose the value for L1/L2/L3 - especially L1?

schematic

simulate this circuit – Schematic created using CircuitLab

Context

This will be the output of the project. The idea is to build a simple temperature sensor for oscilloscope display.

The HPR105 is an isolated switch mode power supply. I think it generate some noise on its outputs. I think an output resistor for OP77 would be a good idea too.

The OP77 has very good performance for this use-case, but I have it in stock.

JRE
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    Whether filtering is useful or not depends on how much noise is acceptable. – Hearth Oct 12 '21 at 15:28
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    Realize that any L-C series circuit can be a potential **resonating** circuit. If I designed this, I would remove the inductors and I would keep the 100 nF capacitors. – Bimpelrekkie Oct 12 '21 at 15:31
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    They can make things worse if not chosen properly. Not like caps where you can usually just keep piling them on and things, at worst, usually stay the same. *Low* resistors are actually safer to use there. – DKNguyen Oct 12 '21 at 15:32
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    *HPR105 is, basically some sort of transformer* You mean: isolated DCDC converter. It has a transformer inside but from the outside it does not behave as a transformer. It is usually a good idea to add capacitors across the input of a DCDC converter. *I guess it should generate some noise to outputs* Yes, **nothing** is without noise. The question is, will the noise disturb anything. My guess is that it will not as long as you remove the inductors. I'm guessing you're a beginner so you worry about too much about noise. Just ignore noise, build this thing (without L1-3) and see what happens. – Bimpelrekkie Oct 12 '21 at 15:36
  • Thanks to you all, So If I don't need very high precision, (*and I do not*), I can ignore L1;L2 & L3. I will do so. –  Oct 12 '21 at 15:47

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