No biggie, just pointing out that there always has been a lack of cross fertilization in the different design fields. I certainly knew about rbb and noise in 1969 from texts like Van der Zeil written in 1962. BUT this one issue is not that big a deal.
"A man should look for what is, and not for what he thinks should be. -Albert Einstein "
What he thinks should be is a good place to start. A man need only have
the intellectual honesty to move on if this does not prove fruitful. There are
those that think that Einstein failed to heed his own advice in later life when
he looked to mathematical beauty as his muse.
😎
What he thinks should be is a good place to start. A man need only have
the intellectual honesty to move on if this does not prove fruitful. There are
those that think that Einstein failed to heed his own advice in later life when
he looked to mathematical beauty as his muse.
😎
LOL!!!
'PFE'
'Proudly found elsewhere'
I have to say John, these are very elegant circuits. 🙂
Sorry, I have been offline for a day, but please look at this chart that came from p.68 of 'Low Noise Electronic Design' , Motchenbacher and Fitchen' 1973.
Unfortunately, while this chart shows a number of 'low noise' devices, it is almost random in its composition.
The BEST comparison is comparing the Rbb' of the 2N4124, NPN; and the 2N4125 PNP. IF you check the spec sheets you will find that these are 'complementary devices, especially using the 2N4126, that is the hi beta select of its part series.
Also note the Rbb' of the 2N4403, PNP transistor that I found in 1978. Note that it is the lowest on the chart.
Personally, I found out from my boss at Ampex instrumentation in 1967, that PNP's were intrinsically quieter than an equivalent NPN, because the PNP has N material in the BASE REGION. Hundreds of tests with the QuanTech have shown this to be true.
Even the Rohm low noise devices have a different Rbb', where the NPN should be 4 ohms and the PNP is 2 ohms as I recall. Anybody have the Rohm data sheets handy?
For the record, I found devices just as quiet as the Rohm from Fairchild in the USA, but I don't know if they are still made.
Unfortunately, while this chart shows a number of 'low noise' devices, it is almost random in its composition.
The BEST comparison is comparing the Rbb' of the 2N4124, NPN; and the 2N4125 PNP. IF you check the spec sheets you will find that these are 'complementary devices, especially using the 2N4126, that is the hi beta select of its part series.
Also note the Rbb' of the 2N4403, PNP transistor that I found in 1978. Note that it is the lowest on the chart.
Personally, I found out from my boss at Ampex instrumentation in 1967, that PNP's were intrinsically quieter than an equivalent NPN, because the PNP has N material in the BASE REGION. Hundreds of tests with the QuanTech have shown this to be true.
Even the Rohm low noise devices have a different Rbb', where the NPN should be 4 ohms and the PNP is 2 ohms as I recall. Anybody have the Rohm data sheets handy?
For the record, I found devices just as quiet as the Rohm from Fairchild in the USA, but I don't know if they are still made.
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John the Fairchild version of a Sanyo part is still around the KSA992 but the data sheet isn't much help without some guessing and calculation. Noise is listed as 25 mV 10 hZ - 1K @ 80 dB in some circuit. I would just measure one though as a professor years ago said to me, why calculate when you can measure. He was also yelling with a large hammer in his hand at the time.
Thanks Capt Grogg, you are correct, but they used to be the PE8050 and the PE8550. Now they appear to be very difficult to find.
NOW, is the SS8550 as low noise as the PE8550? ONLY the QuanTech can tell you quickly. See how valuable it can be?
Sorry, but the KSA992 is NOT an equivalent. It might still work, but it is NOT a direct replacement for a PE5885.
I just suggested the KSA992 on its own not as a replacement for something else. I will have to measure them and see how they look compared to the Rohms and the others you suggested. I don't have a Quantech but I did a circuit board for a modified version of one of Mr Wurcers old noise amplifiers and it works nicely to compare things.
that's pretty funny. reminds me of similar yelling from one of my physics professors who was holding a chair at the time ...
which he eventually threw because he got the wrong answer from the class.
😀
mlloyd1
which he eventually threw because he got the wrong answer from the class.
😀
mlloyd1
Not that it matters much anymore but a gain of 1000 composite amp and your average sound card can do this.
Wayne said:
mlloyd1 said:
These stories were funny to me. Had some professors resort to dramatics to get students' attention.
Scott, do you have the circuit you used for your noise measurements with a sound card? Might make an interesting group PCB design/ buy/ build.
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