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Replies: 29
Views: 17912
I was ordered about 400pcs of these chips in SO8 package from Farnell and from Digikey within some years period. I am using these chips for ultra low distortion audio range sine oscillators manufacturing. But, I need to make noise spectrum measurement control before trying these chips, because situation is non understanding for me in frequency region lower than 100Hz. Only approximately half of all chips has noise density in this region similar as in higher frequency region, but approximately 20% of all chips has very high noise and flicker (more than ten times higher) in this low frequency region. In other ways these chips are very nice, and allow to build oscillators with distortions level about -150dB at 1kHz.
Thank you,
Victor.
In reply to Andy Liu (BMS):
Hi, Andy.
Please advise, if you can, that observed situation is normal, or maybe something is wrong.
Thank you.
In reply to Victor Mickevich:
Hi,
Here are some pictures of spectrum measured in same conditions.
1) very good chips (around 50% of all quantity):
2) good chips (around 30% of all quantity):
3) Noisy chips (around 10% of all quantity). Two pictures from different chips)
4) Very noisy chips (around 10% of all quantity). Three pictures from different chips:
Last chip measured in wider frequency range:
Hi Victor,
In my opinion, if you really care about the "excellent performance in all audio range", I suggest you do the screening by yourself. Sorry, it is not a very good answer, but I cannot offer you a better one.
Andy
I am also seeing burst noise in various production lots of the DIP LME49720 and LME49860. This was observed at the output of a 40 dB gain instrumentation amp input. The NJM5532, NJM2114, NJM2068 and MC33078 do not exhibit this burst noise in the same circuit and same PC board.
It sometimes takes several seconds to occur so if the test time is short, parts with this defect are not screened. This LME49720 sample was a brand-new from the tube lot JR18ABE3.
In reply to Wayne Kirkwood:
Best regards,
Don Dapkus
Gate Driver Applications
Dallas, TX USA
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