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Part Number: LME49710NABD
Good morning to you all.
What I ask is to know if possible the reason why LME49710 inserted as a buffer in the filter of which I enclose the wiring diagram, produces noise in the low pass section of the filter.
In my opinion it is the classic 50/100 Hz noise but I can not be sure because I do not have an analyzer.
The strange fact is that by putting back into the OP27 circuit of AD the noise disappears completely, even with an OPA134PA the noise is non-existent.
In the wiring diagram there are no 10 mF electrolytic capacitors that you suggest to use in the LME49720 datasheet that I have inserted.
Looking for a solution to the problem I noticed that many integrated require measures for their use as a buffer, this also applies to LME49710?
I inserted a double diode bridge in the power supply which I enclose the wiring diagram, and I also replaced the BD139 with a 2SC2660 the noise with OP27 is always inaudible but returns when I replace it with LME49710.
I want to clarify that the other integratiti have always been and are currently the LME49720, also also with the "noise" the sound quality that gives LME49710 is fantastic, the detail is something "super".
I have owned LM325 for years but I think it is time to change, so what can I use to get better nutrition than the current one. As usual, I would like to use only your components that I think are unparalleled.
The LME49710s were bought by me by Mouser.
Thanks for your help.
Sincerely, I greet you
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In reply to Ivan Salazar:
First of all thanks for the interest in my problem.
I add the filter scheme with all the values of the components the cut of the filter is 1500/5000 Hz.
In addition, the power supplies are two for each filter.
Needless to say, I thank you in advance.
In reply to guido bullo48:
In reply to kai klaas69:
The scheme is taken from Progetto Elektor in June 1989, which was the version translated into Italian.
Logically, like all the things that are done in Italy, it was devoid of the value of the components of the filters.
The formulas for its realization I found them randomly on the WEB about ten years ago.
The first thing I want to clarify is the one concerning the noise produced by the integrated ones.
I remembered that I had LME49720 purchased from Digikey, I put them in a channel and to my amazement, the noise was almost imperceptible, so those bought by other suppliers about three years ago were tarots that made me furious for months.
Now I pass to the first question I ask you and it's the one about the value of the resistors!
If the value of the capacitors is triplet, the value of the resistances drops considerably, so the noise could go down a little.
I state that I use Panasonic polypropylene capacitors, exactly the ECW series, what do you think?
For the resistors which can I use?
I currently use the Vishay MRS25000, which ones could I use in the circuit to improve performance.
For the integrated my choice would fall on the OPA134 / OPA2132 series because the OPA1602 series are SMD, they are too small and the printed is almost impossible to make for us car manufacturers.
One thing that I consider very important in light of the facts is to ask Texas to publish photos, or data that make the originals of their components distinguishable, as the copy market is scary and harmful for everyone.
I await your precious advice.
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