lumanauw said:Sometimes, very obvious things can hide beautiful-novel goal, if you think about it deep enough
From what I see, the essence of that patent is about that..........,
BUT it is not just "differential outputs", it is about using the differential outputs...............
WITH very short signal propagation (well, folded cascode is counted as 1 stage).................
TO achieve what?..............
To achieve maximum distortion cancelation with differential outputs.
You make X amp (or differential outputs amp to you) with ordinary 3 stages or more (common differential+2xVAS+2xoutput stage+driver(s) stages), you won't get the same thing with what this patent intended.
Can I check that I'm understanding you correctly? Are you saying that the point of the patent is that with just a single stage, the signal path is shorter and quicker, such that negative feedback reduces distortion more than it otherwise would? (In other words, but put the other way around: the more stages there are, the more delay there is through those stages, the less effective negative feedback is?)
the principle of x has been around well before Nelson came up
with the idea, what he has done is has taken it further by creating
a circuit of his own and in the comercial reality of today's world
where his work could easily be copied he has taken action to
protect his comercial property as it is, it is not about ltp,balance,
supersymmetry, etc... that have been around for ages, as in other
arts where they share similar principles is the work of the particular artist that is protected, and it is that work that is under
threat of copyright abuse
what do you think?
with the idea, what he has done is has taken it further by creating
a circuit of his own and in the comercial reality of today's world
where his work could easily be copied he has taken action to
protect his comercial property as it is, it is not about ltp,balance,
supersymmetry, etc... that have been around for ages, as in other
arts where they share similar principles is the work of the particular artist that is protected, and it is that work that is under
threat of copyright abuse
what do you think?
Hi, Simon,
Why is this "something"? Because it is hard to achieve such a distortion elimination like this patent does. With ordinary 3 stages (or more) plain vanilla topology, you will never achieve the same result. Remember, that feedback works effectively for lower order distortion, and starting losing control over higher order distortion. Adding more stages+feedback will result in higher order ones, which feedback cannot eliminate. Why? Because transistor's curve is not linear, it is "curved". It cannot eliminate higher order distortion, but works fine for lower order ones.
If you look at the transfer function of 1 transistor, it is pretty complex equation, isn't it? The equation between output vs input. Putting another stage means you put this complex transfer function into another complex transfer. The result is "complex"x"complex". Making many stages with non-linear device is making very complex transfer function between output vs input. The differential is just 2 transistor connected in it's emitor. It will have limited capability of distortion reduction when headed to very complex transfer fuction.
BUT the harmonic pattern changes. Usually shifting the lower order ones to higher order ones with more stages+feedback. The signal is "forced" to get minimum delay in the output node, while naturally without feedback, it wants to have some delay (due to capacitance inside transistor or anywhere).
In general, yes, it is right. The feedback works very effective for minimal stages.The X mode effectively adds more of common mode distortion reduction. This fits in, because in X amp, you need less gain for each half to make the intended total gain of the amp. Less stage(s) means less OL gain, but this is just the right situation.
Why is this "something"? Because it is hard to achieve such a distortion elimination like this patent does. With ordinary 3 stages (or more) plain vanilla topology, you will never achieve the same result. Remember, that feedback works effectively for lower order distortion, and starting losing control over higher order distortion. Adding more stages+feedback will result in higher order ones, which feedback cannot eliminate. Why? Because transistor's curve is not linear, it is "curved". It cannot eliminate higher order distortion, but works fine for lower order ones.
If you look at the transfer function of 1 transistor, it is pretty complex equation, isn't it? The equation between output vs input. Putting another stage means you put this complex transfer function into another complex transfer. The result is "complex"x"complex". Making many stages with non-linear device is making very complex transfer function between output vs input. The differential is just 2 transistor connected in it's emitor. It will have limited capability of distortion reduction when headed to very complex transfer fuction.
Not quite like that. Whenever there is feedback, there is much less delay than when it is run openloop. The feedback central (differential) wouldn't allow delay, otherwise in differential's transistor the base signal and the emitor/collector signal is not in phase, which is impossible. The differential dictates that even many stages amp will exhibit much less delay than if it is run openloop.
BUT the harmonic pattern changes. Usually shifting the lower order ones to higher order ones with more stages+feedback. The signal is "forced" to get minimum delay in the output node, while naturally without feedback, it wants to have some delay (due to capacitance inside transistor or anywhere).
Joe Berry said:
Yes, that does help, thanks
Trouble is, you're not going to measure anything common-mode that way. When measuring the distortion/error/whatever across the output terminals, you won't be measuring anything they have in common, because you're measuring the difference. Anything that's common to both outputs will be subtracted in the way the measurement itself is made.Or did you mean a common-mode error elsewhere (such as in the inputs) that manifests itself differentially at the outputs?
Anyway, I'll re-read your earlier post in light of your clarification...
Okay, I've re-read it, but I'm still unclear. What is the common-mode error you were on about? Was it unwanted, common-mode components of the input?
lumanauw said:
Hello!
Not so. I just hadn't read Joe Berry's comment, yet. (But I have now.)
Do you mean I've actually got to listen for the difference? Or measure it with scopes and stuff?
I'm afraid that won't do
The patent is for the invention itself, not for how the invention happens to sound when compared with others.For the patent to be valid, the patentee had to disclose, in the patent application, something new and non-obvious that constitutes a patentable invention under patent law. That means there's got to be something that was new and non-obvious about the circuits themselves, as it's those circuits that are the inventions.
Patents, not Copyright
Firstly, patents and copyright are different things. You're on about copyright, but I'm on about a patent.
Secondly, from what you've said about "the principle of x [having] been around well before Nelson came up with the idea", it seems the patent is, indeed, invalid. (For the patent to be valid, it's not enough for Pass' amplifiers to be his own work, they've also got to constitute a patentable invention under patent law.)
mastertech said:
Firstly, patents and copyright are different things. You're on about copyright, but I'm on about a patent.
Secondly, from what you've said about "the principle of x [having] been around well before Nelson came up with the idea", it seems the patent is, indeed, invalid. (For the patent to be valid, it's not enough for Pass' amplifiers to be his own work, they've also got to constitute a patentable invention under patent law.)
Hi, Simon,
Sometimes listening to the difference is enough to know the difference But if you got complete measurement equipment, you can see more, offcourse, IF you got a proper measurement that can detect what makes the difference.
If the patent is about how it will "sound/measurement result" compared the "sound/measurement result" known so far, maybe the only way is to compare the result by listening/masuring the real cct of what being patented, to know what is being patented for. Audio electronics is difficult, you cannot know how a cct (even a simplest one) will sound, just by looking at the schematic
You give a difficult case IF the patent officer is smarter than Nelson Pass, he can judge wheter a certain patent is eligible or not, but it's very hard to find a man smarter than NP that works in patent office
If you see a transistor, it has 3 legs, isn't it? If it only got 3 legs, like NP said, it has maybe only 3 way to use it, common base, common emitor or common collector.
From the year the transistor is invented (I think it's before1950's) every basic way to use a transistor have been found.
Around that years, major basic transistor usage for audio amps have invented, even classD.
So, what's left for people after 1950's to wrote a patent about audio amps using transistor? The only thing left is how to combine those techniques (which have been found) to get "something new". This "something new" maybe a "way" to get minimum distortion, or a "way" of controlling bias, or a "way" of something........, but couldn't be the very basic ideas.
The SuSy patent is more about a "way" to reduce distortion, not about inventing a new technique making cct. It is achieved by combining everything that has been known from the past inventions.
Now is 2005, people still patenting something about analog audio power amps. If you see them, almost all of them is about how to "combine" the basic cct's to get a "new" "way" of something.......
Sometimes listening to the difference is enough to know the difference
But if you got complete measurement equipment, you can see more, offcourse, IF you got a proper measurement that can detect what makes the difference. If the patent is about how it will "sound/measurement result" compared the "sound/measurement result" known so far, maybe the only way is to compare the result by listening/masuring the real cct of what being patented, to know what is being patented for. Audio electronics is difficult, you cannot know how a cct (even a simplest one) will sound, just by looking at the schematic
You give a difficult case
IF the patent officer is smarter than Nelson Pass, he can judge wheter a certain patent is eligible or not, but it's very hard to find a man smarter than NP that works in patent office If you see a transistor, it has 3 legs, isn't it? If it only got 3 legs, like NP said, it has maybe only 3 way to use it, common base, common emitor or common collector.
From the year the transistor is invented (I think it's before1950's) every basic way to use a transistor have been found.
Around that years, major basic transistor usage for audio amps have invented, even classD.
So, what's left for people after 1950's to wrote a patent about audio amps using transistor? The only thing left is how to combine those techniques (which have been found) to get "something new". This "something new" maybe a "way" to get minimum distortion, or a "way" of controlling bias, or a "way" of something........, but couldn't be the very basic ideas.
The SuSy patent is more about a "way" to reduce distortion, not about inventing a new technique making cct. It is achieved by combining everything that has been known from the past inventions.
Now is 2005, people still patenting something about analog audio power amps. If you see them, almost all of them is about how to "combine" the basic cct's to get a "new" "way" of something.......
moe29 said:
I'm not trying to bash either Pass or the US PTO. (But even if I was, that wouldn't make the patent valid.) My question, 'what am I missing?', is not rhetorical. I'm assuming the patent is valid. I'm just having terrible difficulty seeing what was new and non-obvious about the claimed invention(s).
Or, to put it another way, I'm assuming the Emperor is wearing clothes, but, for some reason, I've failed to see them. Perhaps I'm standing in the wrong place, and can't even see the Emperor from where I'm standing (maybe there's a pillar in the way, for example). Or maybe I'm blind in some way (but in a way that doesn't afflict my ability to see how long-tailed pairs work, and the like). So, finding myself unable to see the Emperor's clothes directly when I look myself, I'm asking: what are the Emperor's new clothes?
Or, to put it yet another way, I'm trying to 'spot the difference', but I keep failing, only seeing the things that are (or at least appear to me to be) the same.
So I'm asking: what have I missed? What have I overlooked? What have I misunderstood?
Perhaps you, moe29, could enlighten me, and tell me what the Emperor's wearing? (Even if I am a basher/flamer/troll/whatever, other readers who are genuinely wondering similar things might find it helpful.) Or, like me, do you not know, either?
Thanks, lumanauw, for your post
I'm afraid I still don't see the novelty/non-obviousness of it, though. If you can have multistage amplifiers, you can obviously have single stage ones (otherwise: what are you going to build multistage amplifiers out of?). And if you can apply negative feedback to amplifiers, you can obviously apply it to single stage amplifiers (because they're amplifiers, to which negative feedback can be applied). And the idea of having as few stages as possible, in order to introduce as little distortion as possible (as well as to avoid problems with feedback over multiple stages (stability, high-frequency oscillations, etc)), was surely more than just well-known in audiophilia (and electronic engineering generally), and has been for a long time.
Having said that, if the amplifier itself (not including the negative feedback that's then applied) was somehow new and non-obvious (in how it makes use of negative feedback when negative feedback is applied, etc), then yes, no problem! Is that what it is? Is that what I'm missing?
Now that we're clearly looking at just having a single stage, with differential inputs, and differential outputs, with negative feedback applied on both sides, with the two sides being as symmetrical as possible, I think my question really does boil down to this: how is it neither a long-tailed pair, nor a simple, obvious or old equivalent or variation of a long-tailed pair?
Is the difference in the tail (or equivalent, or whatever it is)? Is it in each pair, not including the tail (such as the folded cascodes)? Is it something else?
Or, to put it another way:-
Let's suppose I design and build an amplifier, which I then sell, commercially, in the US. Let's also suppose that this amplifier, being aimed at the audiophile market, is as simple as I can make it - just one stage. It's got differential inputs, and differential outputs, and is, in fact, just a long-tailed pair with negative feedback applied (on both sides, obviously). Oh, and it's built out of MOSFETs, so as to avoid the need for multiple current-amplifying stages. What are the differences between Pass' amplifiers and mine that mean I wouldn't be infringing his patent?
I'm afraid I still don't see the novelty/non-obviousness of it, though. If you can have multistage amplifiers, you can obviously have single stage ones (otherwise: what are you going to build multistage amplifiers out of?). And if you can apply negative feedback to amplifiers, you can obviously apply it to single stage amplifiers (because they're amplifiers, to which negative feedback can be applied). And the idea of having as few stages as possible, in order to introduce as little distortion as possible (as well as to avoid problems with feedback over multiple stages (stability, high-frequency oscillations, etc)), was surely more than just well-known in audiophilia (and electronic engineering generally), and has been for a long time.
Having said that, if the amplifier itself (not including the negative feedback that's then applied) was somehow new and non-obvious (in how it makes use of negative feedback when negative feedback is applied, etc), then yes, no problem! Is that what it is? Is that what I'm missing?
Now that we're clearly looking at just having a single stage, with differential inputs, and differential outputs, with negative feedback applied on both sides, with the two sides being as symmetrical as possible, I think my question really does boil down to this: how is it neither a long-tailed pair, nor a simple, obvious or old equivalent or variation of a long-tailed pair?
Is the difference in the tail (or equivalent, or whatever it is)? Is it in each pair, not including the tail (such as the folded cascodes)? Is it something else?
Or, to put it another way:-
Let's suppose I design and build an amplifier, which I then sell, commercially, in the US. Let's also suppose that this amplifier, being aimed at the audiophile market, is as simple as I can make it - just one stage. It's got differential inputs, and differential outputs, and is, in fact, just a long-tailed pair with negative feedback applied (on both sides, obviously). Oh, and it's built out of MOSFETs, so as to avoid the need for multiple current-amplifying stages. What are the differences between Pass' amplifiers and mine that mean I wouldn't be infringing his patent?
Not a lawyer, usual disclaimer, but I've been through the patent system many, many times, in application, prosecution, and litigation.
Basic rule:
A patent is as strong as the ability of the patent holder to pay for expensive litigation compared to the accused infringer's ability to pay for expensive litigation. No more and no less.
All inventions involve combining previous inventions. Whether something is "obvious" or not is a judgement call and can vary greatly from examiner to examiner. Once it's past the examiner, it is a judgement call by a judge, after each participant in the suit has shelled out half a million dollars (for a small case). Trying to look at a legal process by engineering thinking is inappropriate.
BTW, regarding you comment on the intelligence of examiners, I've encountered a pretty wide range. The best of them were exceptionally smart people. I understand that the Swiss patent office had a young fell named Einstein working there...
Basic rule:
A patent is as strong as the ability of the patent holder to pay for expensive litigation compared to the accused infringer's ability to pay for expensive litigation. No more and no less.
All inventions involve combining previous inventions. Whether something is "obvious" or not is a judgement call and can vary greatly from examiner to examiner. Once it's past the examiner, it is a judgement call by a judge, after each participant in the suit has shelled out half a million dollars (for a small case). Trying to look at a legal process by engineering thinking is inappropriate.
BTW, regarding you comment on the intelligence of examiners, I've encountered a pretty wide range. The best of them were exceptionally smart people. I understand that the Swiss patent office had a young fell named Einstein working there...
Hi, Simon,
In the original SuSy patent, NP doesn't use differential (as LTP), he uses 2 independent common emitor based folded cascode amp, bridged (not as tightly as a "differential") by 1 resistor, bridging these 2 common emitor systems.
As for the rest of your upper post, I really (no joke) cannot capture your point. I don't use English in my daily life here, so pardon me
You're welcome
In the original SuSy patent, NP doesn't use differential (as LTP), he uses 2 independent common emitor based folded cascode amp, bridged (not as tightly as a "differential") by 1 resistor, bridging these 2 common emitor systems.
As for the rest of your upper post, I really (no joke) cannot capture your point. I don't use English in my daily life here, so pardon me
lumanauw said:
Hello, again. I think we're converging onto the same wavelength (or something like that)
If the patent is about how it will "sound/measurement result" compared the "sound/measurement result" known so far, maybe the only way is to compare the result by listening/masuring the real cct of what being patented, to know what is being patented for. Audio electronics is difficult, you cannot know how a cct (even a simplest one) will sound, just by looking at the schematic
The patent is for the amplifiers themselves. The claims section goes like this:-
It's all amplifier circuits. That's what Pass claimed, that's what the patent's for.
IF the patent officer is smarter than Nelson Pass, he can judge wheter a certain patent is eligible or not, but it's very hard to find a man smarter than NP that works in patent office
I don't doubt it.
Yep! It's that "something new" I'm looking for.
Yep, that's what it has to be. And, whatever that "way" is, it has to be disclosed in the patent application.
Of course.
But it's not enough for something to be new, it's also got to be non-obvious to someone competent in the relevant art/field.
They are at the input but not part of the input signal. Rather, they are common-mode noise and distortion added by the amplifier (including the input diff pair) and returned to the differential inputs via the NFB loop. The input differential pair can't “see” these components because of its own high common-mode rejection, so it cannot correct for them at the output.
Of course that's true, and I can see that my earlier description was confusing on this point. A more accurate description, at least according to my understanding, might be that the x feedback results in the conversion of differential error terms to common-mode terms which are then rejected by the load. This conversion, as I understand it, takes place in the input differential pair, which acts as a summing and transfer point for the residual distortions appearing at each input.
my disclaimer, I am a lawyer, but not a patent attorney
Simon listed a variety of techniques that were known at the time the patent was issued. and wondered why SuSy was patentable. Some of it has to do with the novelty of the combination of ideas, some of it has to do with what is claimed.
An example of another patent that seemed very obvious to me was granted to Cannondale for their idea of using large diameter thin gauge aluminum tubing to make abicycle frame >30% stiffer than a traditional frame while being lightweight (without looking it up I believe they claimed weight saving relative to the then traditional steel frame). It was well known that large tubes can be stiffer, and thin gauge tubes are lighter. At the time, other aluminum frame makers were starting to increase the diameter of their tubes to make them stiffer. What was the novel idea in the patent? The >30% stiffer bicycle frame claim. Klein lost a suit when they made their frames as stiff as a Cannondale. They had to change their specifications slightly to be less than 30% stiffer.
The obviousness test is difficult to quantify. Many patented inventions seem so obvious when you see them. One way to look at it is what is your reaction? Is it something like "no kidding" or "I wish I had thought of that"? If the former AT THE TIME THE PATENT IS EXAMINED it probably isn't novel. Just becasue you have that same reaction ten years later really doesn't matter as far as patentability.
As applies to the SuSy Patent, NP claims a circuit arrangment that reduces common mode distortion to a greater extent than traditional negative feedback techniques would imply AND he got his claim to the Patent Office before anyone else did. In addition to the crossed global NFB loops, I believe that he also claimed that teh connection of the sources of the input devices provided some additional distortion reduction (look at it as two single ended input amps connected with the input device sources connected) How this differs from the distortion cancellation normally found in a differential pair, I am not qualified to say.
You can argue about it all you want - as Sy said, until you step up to the plate with a million dollars and standing to challenge the patent, the point is moot. (Standing means a reason to challenge, like you have an amp design that Pass claims infringes the patent you want to put in production)
I guess it boils down to a business decision: Can I get a license and make money, is it cheaper to design around the patent, challenge it or am I the 800 pound gorilla who can litigate long enough put the small patent owner into bankruptcy and then buy the patent for pennies on the dollar.
Mr Pass could have chosen to not patent his invention, nad just kept them trade secrets. He could have potted his boards to limit reverese engineering and not published his schematics. I am glad he chose to go the patent route and share his ideas with the DIY community. Thank You Mr. Pass
Simon listed a variety of techniques that were known at the time the patent was issued. and wondered why SuSy was patentable. Some of it has to do with the novelty of the combination of ideas, some of it has to do with what is claimed.
An example of another patent that seemed very obvious to me was granted to Cannondale for their idea of using large diameter thin gauge aluminum tubing to make abicycle frame >30% stiffer than a traditional frame while being lightweight (without looking it up I believe they claimed weight saving relative to the then traditional steel frame). It was well known that large tubes can be stiffer, and thin gauge tubes are lighter. At the time, other aluminum frame makers were starting to increase the diameter of their tubes to make them stiffer. What was the novel idea in the patent? The >30% stiffer bicycle frame claim. Klein lost a suit when they made their frames as stiff as a Cannondale. They had to change their specifications slightly to be less than 30% stiffer.
The obviousness test is difficult to quantify. Many patented inventions seem so obvious when you see them. One way to look at it is what is your reaction? Is it something like "no kidding" or "I wish I had thought of that"? If the former AT THE TIME THE PATENT IS EXAMINED it probably isn't novel. Just becasue you have that same reaction ten years later really doesn't matter as far as patentability.
As applies to the SuSy Patent, NP claims a circuit arrangment that reduces common mode distortion to a greater extent than traditional negative feedback techniques would imply AND he got his claim to the Patent Office before anyone else did. In addition to the crossed global NFB loops, I believe that he also claimed that teh connection of the sources of the input devices provided some additional distortion reduction (look at it as two single ended input amps connected with the input device sources connected) How this differs from the distortion cancellation normally found in a differential pair, I am not qualified to say.
You can argue about it all you want - as Sy said, until you step up to the plate with a million dollars and standing to challenge the patent, the point is moot. (Standing means a reason to challenge, like you have an amp design that Pass claims infringes the patent you want to put in production)
I guess it boils down to a business decision: Can I get a license and make money, is it cheaper to design around the patent, challenge it or am I the 800 pound gorilla who can litigate long enough put the small patent owner into bankruptcy and then buy the patent for pennies on the dollar.
Mr Pass could have chosen to not patent his invention, nad just kept them trade secrets. He could have potted his boards to limit reverese engineering and not published his schematics. I am glad he chose to go the patent route and share his ideas with the DIY community. Thank You Mr. Pass
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