I missed that, thanks! Well, on the other jfet I guess I go for the Chinese jfets and cross my fingers!
open loop performances of the DB-CM-DB architecture are quite amazing
Under simulation at any rate, my results bear this out 100%.
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It seems that NTE457/NTE460 by NTE Electronics are equivalent to 2N5457/2N5460 - Newark has a few of them in stock.
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Thx I'll get some and check them on the curve tracer to see how close they are to the ones I used. Got the ones i used very cheap on Internet (like, 12 cents). -RNM
I have a lot of those types here - all sorted by Idss groups. Didnt want the high non-linear input C so I didnt try them. Let me know how it goes.
I interpreted "open loop" as "the output buffer is outside the feedback loop" rather than "there is no return current into the inverting input". I guess that was incorrect.
If you remove R6 completely however, things go a little screwy since the impedance of that node just jumps up to the remaining components surrounding it (Q13,Q14) - gain goes up (roughly 45 dB), distortion goes up, bandwidth goes down.
It is possible to run "open loop" by dismantling the feedback connection, connecting R6 to ground instead of R5. The simulated performance is largely unchanged.
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psst... Complement. You do this mistake in the article too.
Jan, note it for reprint
yep. Compliment, for example, would mean to say something nice about you. Just another reason not to rely on the computers spell checker only. Thx
forr - I hadn't heard the term before, but on searching, it certainly seems to be a variant thereof.
coluke - and works it does, but I still don't understand why you'd choose that connection scheme (grounded) over the other (back to the front half of the current mirror). Seems to me like there is no difference.
rnmarsh - no, not yet. I'm not even sure what I should be "optimizing", even.
coluke - and works it does, but I still don't understand why you'd choose that connection scheme (grounded) over the other (back to the front half of the current mirror). Seems to me like there is no difference.
rnmarsh - no, not yet. I'm not even sure what I should be "optimizing", even.
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Here are my own modest base requirements for a line stage (similar for power amp):
1. Open loop BW of 40KHz or more (-3dB)... 20KHz min.
2. IM and THD of less than .001% at 1v rms into 30 ohms for any frequency between 20Hz and 20KHz.
3. No coupling caps on input or output or in feedback path.
4. No use of dc servo circuits to track and correct dc offset and drift.
5. No more than 6-8 transistors (excluding power supply).
6. S/N ref 1 volt rms and without weighting of at least -130dB (input can be shorted or terminated).
7. No significant harmonics above the 2nd and 3rd.
8. Closed loop gain between 12 and 20 dBv
9. Low Zout (less than a fraction of an Ohm at any audio freq).
10. Distortion not be changed by source Z.
11. Transistors should be low cost and not be exotic, hard to obtain, very expensive or no longer manufactured.
There might be a thing or two I missed, off the top of my head, but this is do-able and should be done in all audio circuits IMHO. -RNM
