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Old 19th August 2004, 06:20 PM   #1
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Question Low noise transistor and noise figur

Any suggestions for SMD input transistors with very low noise?

Have someone seen a manufactor besides Sanyo that have noise figure plots in there datasheet?
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Old 20th August 2004, 10:55 AM   #2
hjelm is offline hjelm  Sweden
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Infineon BCW60 and BCW61; BC850 BC860; BC846 BC856;
Phillips BC850 BC860
The infineon ones have noise graphs plotted, look at the homepage under AF transistors, they are not all under low noise rather general purpose.
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Old 20th August 2004, 10:57 AM   #3
hjelm is offline hjelm  Sweden
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Forgot Toshiba SA970 and SC2240. Their datasheets have a lot of information.
Edit: Sorry ignore these since they are not SMD
Edit again: Toshiba has low noise SMD transistors with noise graphs check Toshiba
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Old 20th August 2004, 02:19 PM   #4
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Also you can check with Zetex, then you can find what you need there.....
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Old 20th August 2004, 03:12 PM   #5
jcx is offline jcx  United States
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you are aware that noise figure is essentially useless for low noise audio design?

national semiconductors an-104 and 222 are worth reading
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Old 20th August 2004, 03:40 PM   #6
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Default Re: Low noise transistor and noise figur

Quote:
Originally posted by Real_Macgyver
Any suggestions for SMD input transistors with very low noise?

Have someone seen a manufactor besides Sanyo that have noise figure plots in there datasheet?
Unless you are planning a MC preamp or a mic amp you don't need anything more low noise than plain BC850 types, This transistor gives you around 1 uV input noise wihich is sufficient down to MM phono amps. Anything above that aren't very critical when it comes to noise if you design to minize the noise with those parts you have got.
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Old 20th August 2004, 03:55 PM   #7
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The lowest noise audio types i have ever seen are ROHM 2SA1455k and 2SC3722k they have a noise figure of just 0,2 dB. They are suitable for normal line level impedances like 1 - 22k.

If you are looking to build an MC amp, you should use other types, like the 2SB737 and 2SD786. They have a super low noise but only if the load impedance is low (as is the case in an MC amp).
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Old 20th August 2004, 04:08 PM   #8
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If we talk about it, SSM2210 and SSM2220 from Analog Devices are also OK but they have other unwanted properties (you can't have it all)
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Old 21st August 2004, 12:22 AM   #9
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Quote:
Originally posted by Lars Clausen
The lowest noise audio types i have ever seen are ROHM 2SA1455k and 2SC3722k they have a noise figure of just 0,2 dB. They are suitable for normal line level impedances like 1 - 22k.

If you are looking to build an MC amp, you should use other types, like the 2SB737 and 2SD786. They have a super low noise but only if the load impedance is low (as is the case in an MC amp).
Thanks Lars. Wasn't aware of these devices. Do you know where
to locate data sheet for 1455k & 3722k?


Cheers,

Terry
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Old 21st August 2004, 12:48 AM   #10
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I thought Rohm discontinued the 2SB737/2SD786.
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