Dr. Marshal Leach wrote an article on low noise design for the Proceedings IEEE, Oct. 1994, titled "Fundamentals of Low-Noise Analog Circuit design". It's more theoretical than the Netzer article but very good.
@AMMEL68
Did you consider using the Texas Instruments LM6121?
http://www.ti.com/lit/ds/symlink/lm6221.pdf
@AMMEL68
Did you consider using the Texas Instruments LM6121?
http://www.ti.com/lit/ds/symlink/lm6221.pdf
No, I have never tried the 6121.
Looks as though they've been discontinued, unless you know of a source.
I have that one... I already tested it also but it isnt as quiet as many others. If you need the numbers for SIM models, I can give it to you but it isnt a good low noise transistor at 1-3mA. It may have other redeeming qualities.
THx-RNMarsh
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Forgot to include a link to the noise article by Professor Leach.
http://users.ece.gatech.edu/~mleach/papers/AnalogNoise.pdf
ammel68,
You can probably locate some NOS or a replacement. I used the LH0002 in filters 30 years ago and they were discontinued but they were so popular that another company made a replacement.
MSK0002 General Purpose Current Amplifier Designed and Made by MS Kennedy
http://users.ece.gatech.edu/~mleach/papers/AnalogNoise.pdf
ammel68,
You can probably locate some NOS or a replacement. I used the LH0002 in filters 30 years ago and they were discontinued but they were so popular that another company made a replacement.
MSK0002 General Purpose Current Amplifier Designed and Made by MS Kennedy
Not sure where it's from, but I'm not crazy about the 10uF caps on the outputs of the buffers.
It's the MF trivista dac,
Yes I think the caps can be eliminated by carefull adjustment of the dc offset, but it still had a small switch on bump.
I've shown how to do this on the same/ different model which has the same output stage, the MF A3-24 a few years back in another thread, with circuit diagram. But then this one has tube input so it may not be successful
Cheers George
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Mr. Marsh,
If you have a 2N4250 in you stock, please show noise results. The reason I ask is because years ago I was looking for that transistor and found it in the Central Semiconductor catalog. Central Semiconductor told me the 2N4250 part number was obsolete and to use 2N5087 instead. I'm interested in a comparison.
If you have a 2N4250 in you stock, please show noise results. The reason I ask is because years ago I was looking for that transistor and found it in the Central Semiconductor catalog. Central Semiconductor told me the 2N4250 part number was obsolete and to use 2N5087 instead. I'm interested in a comparison.
2N5087 is PNP, the original complement was the 2N5089 but the 2N5210 became a better choice. So those would be the righ ones to compare to a 2N2222
The issue with most of the transistors under discussion was that I believe they are straight NPN or PNP construction so the beta vs current curve is not very flat. Of course when used with a current source that is not much of an issue.
Later transistor designs are more complex to prevent base spreading among other improvements.
I still keep all of these in stock and use them.
Richard is almost convincing me to get a Quantech, although I probably will try a few other techniques first. Maybe even build a modern DIY version. Of course I am overloaded with work for now.