| Netlist |
Another gem. And for simple souls like me, the analogy with the runner is a very understandable one.
Thank you…again.
/Hugo |
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| bogdan_borko |
| THANKS A LOT!:) |
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| fredlock |
Thanks Nelson for sharing us this bias current article. I was enlightened with some of the questions on my head. :bulb: :cheerful:
More power to you.
Freddie |
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| Dennis Hui |
Dear Mr. Pass,
Thank you for another fun read!
Cheers,
Dennis |
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| lordvader |
Scared the **** out of me !!!
For a second I thought you were actually leaving class-a and moving on ... |
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| mpmarino |
| quote: | Originally posted by lordvader
Scared the **** out of me !!!
For a second I thought you were actually leaving class-a and moving on ... |
-only when he invents a new class that makes even more heat
:clown:
Nice article ;) |
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| chinsettawong |
Thank you, Mr. Pass.
Wachara C. |
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| jacco vermeulen |
Leaving ? But i just entered.
The 100.5 numbers are nice.
Why, next thing you know the FB folks will be forcing their PP-OP into SE. |
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| Manu |
Very enjoyable article,
Thanks a lot Mr. Pass
Manu |
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| cfcubed |
Wanted to add my thanks for the article too... Being new to this, articles like that sure help.
Wonder if the "Our meters don’t go to zero." bit is akin to the Spinal Tap volume 11 bit :D |
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| MEH |
| Is there a general principle that can be stated about the relative quality of generating overall bias current X through n devices vs. through m devices where n < m? |
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| EUVL |
I found Fig.4 particularly interesting, and presume they showed the distortion of a single pair of complementary devices at the said bias current.
I wonder what the distortion would look like if the same bias current is shared between say 4 pairs of the same devices in parallel, each device only take 1/4 of the bias current as in Fig.4.
Would you perhaps care to comment on this ?
Patrick |
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| MEH |
| Hey! That's my question! |
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| Nelson Pass |
This question is commonly asked. Certainly the performance is
not identical for both cases, but there is a cancellation factor.
With parallel devices the transconductance as a whole goes up,
lowering the distortion because the variation per device is lower
by virtue of sharing the current.
At the same time, if the bias is divided between devices, the
distortion per device goes up.
The two effects do not give an exact cancellation, but it's close
enough that for most applications you can decide on the number
of parallel devices based on dissipation needs.
One factor that tends to favor parallel devices is that the
total bias dissipation can be larger even for the same size heat
sink, since there's less aggregate thermal resistance from the
junctions to the sink. |
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| Nelson Pass |
| quote: | Originally posted by cfcubed
Wonder if the "Our meters don’t go to zero." bit is akin to the Spinal Tap volume 11 bit :D |
Exactly where it came from. |
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| EUVL |
> The two effects do not give an exact cancellation, but it's close enough that for most applications you can decide on the number of parallel devices based on dissipation needs.
Perhaps the distortion level is comparable, but how about the spectrum -- does the ratio between say 2nd, 3rd, 4th remain largerly the same, or do they shift one way or another ?
Patrick |
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| Vix |
"Klunk!" -Your amplifier has just left class A operation! Consequently, small aliens will invade the transistors in your amp, generating distortion. Hence you will experience an instant decrease of sound quality, depriving you of listening pleasures, which may have side effects, such as insomnia. Consequently, you will have only two choices. First, you may turn down the volume (that you don't want), or, burn mo' power, to keep the green aliens away. If this statement does not make any sense to you, please go back to post nr.1 of this thread and read the paper. "Klunk"! :rofl: :rofl: :rofl:
No, seriously, nice paper. :cool: By the way, if we connect more devices parallel, the capacitance also increases, making the output more difficult to drive? |
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| Manu |
Mr. Pass, dear Papa,
referring to page 7, you suggest a ccs as best SE Bias for PP topology. What would you advocate instead of a Res to V- solution ...?
Manu |
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| Nelson Pass |
| The resistor works fine as long as the supply isn't too noisy. |
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| jacco vermeulen |
| quote: | Originally posted by Manu
advocate |
Chico,
regarde Ca |
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| Zen Mod |
| quote: | Originally posted by Vix
........
No, seriously, nice paper. :cool: By the way, if we connect more devices parallel, the capacitance also increases, making the output more difficult to drive? |
you must count on increased xconductance , with more outputs , so that ratio between No. of devices/difficulty to drive isn't quite linear |
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| Nelson Pass |
The part that is linear is the Cgd, which is quite a bit smaller than
Cgs. Driving Cgs has the same compensating effect - there's more
Cgs to drive, but it takes less voltage to drive it. |
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| Vix |
Thanks!
I got it. More is more :) :cool: |
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| Manu |
| quote: | Originally posted by Nelson Pass
The resistor works fine as long as the supply isn't too noisy. |
Thanks!
But I need some more help to understand :
What would be exactly the effect of a "noisy" supply?
| quote: | Originally posted by jacco vermeulen
Chico,
regarde Ca |
Jacco-the-brain : sincerely admire your memory, amazing...
Thanks for link ... but in defence of my inattention I must say I was not really aware of this question. Usually you don't see what you don't know...
Manu |
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| Nelson Pass |
| quote: | Originally posted by Manu
But I need some more help to understand :
What would be exactly the effect of a "noisy" supply? |
The resistor to the supply conducts not only DC but also AC, so any
noise on the supply is injected into the output. |
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| Manu |
Thats very clear now, thank you very much ...
Manu |
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| tryonziess |
Nelson, The increased bias current is shown to be a major improvement by the graphs provided. Is there any correlation that relates to the actual heat of the output devices. Does this heat which is causing the molecular particles to move faster attribute any advantages? I know there is a practical limit here.
Very nice article, makes things much easier to understand. Tad |
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| Nelson Pass |
There is a subtle performance difference with devices running a
little hotter, but mostly we make sure that we do all our adjustments
at normal operating temperature, and that means that we often have
to re-adjust after warm-up and burn-in. |
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| kzim229 |
| I love this site. |
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| Nelson Pass |
Yeah, me too.
:cool: |
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| lineup |
| quote: | | Originally posted by Nelson Pass Yeah, me too. |
mee to |
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