Please don't refer to the 5A as bias. That is part of what caused so much confusion earlier.
Each half of the balanced F5 is biased to Xamps, describes it correctly and unambiguously.
Yes, 2pair in each half requiring 8 output devices to drive the 4ohm speaker in ClassA.
and that gives Pq=~260W, +-25Vdc and biased to 2.6A
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When I have difficulty understanding something, I usually
keep it in front of me until I absorb it through osmosis.
With all due respect, Mr Pass...... The last time I had osmosis, it only resulted in water damage and black mold in my bathroom's subflooring. Therein, I guess, lies the difference between you and me..........
I wish people would read. I said ASSUMING NO LOSSES
Well you can't do it with one pair. So it is either 2 pairs (one pair per half), or 4pairs etc. You can do as many pairs as you want but the total bias remains the same.
Hi Andrew, I don't know if it is just me but I think you are the only one confused. 5A total is 5A total. You simply divide it by the number of out put pairs you have.
First, one should never assume (*** + u + me). That notwithstanding, with no losses, you should be able to use all of that 20A rating of an IRFP240!
I know its taken out of 'context', sorry
but, its showing one aspect of the 'problem'
each individual transistor needs a minimum of bias/idle, yes ?
I remember the question, when we started out on this 'jouney' with multiple outputs(maybe a year ago)
and how do you plan to bias each output transistor
that question put me in back-off mode, rethinking it all
well, I guess I'm still in the 'osmosis state' on that one
First, one should never assume (*** + u + me). That notwithstanding, with no losses, you should be able to use all of that 20A rating of an IRFP240!
Well when you learn this stuff at university you make lots of assumptions to make the learning and maths easier. As long as you state what the assumptions are there is no problem.
Here are some examples of that "Assume friction=0", "Assume no wind resistance", "Assume no IR losses" etc.
Instead of arguing and confusing the hell out of everyone how about finding points to agree on and then adding your own bit.
eg "Yes, assuming no losses, 20V is correct. If we take losses into consideration (eg 2V-4V) then we need 22V to 24V rails to get our 25W standard F5 and 100W balanced F5"
It seems like people go out of their way to disagree with each other when in actual fact, they agree on quite a lot.
Just sharing the cause of my frustration
apart from the high power one, I found your calculation very clear 
I dont see any confusion
its true, some will eat anything raw
maybe even order trafos for 20V rails
but nothing you can do about that
other than suggest to read the manual first
should clear all misunderstandings
anyway, 20V rails might not be so bad at all, with more bias/idle current
I dont see any confusion
its true, some will eat anything raw
maybe even order trafos for 20V rails
but nothing you can do about that
other than suggest to read the manual first
should clear all misunderstandings
anyway, 20V rails might not be so bad at all, with more bias/idle current
Melon Head, what I said was all in fun. Obviously. But in terms of real, get the point across, I'm feeling realy sorry lately. You and others have seen the onrush of New-B attitudes that insult, wine and what ever, the people who try to help them. From Patrick to Tinitus. But somehow kissing N.P.'s a** is cool We are not all jumping in, because we are seasoned and we know better. Someone who barely knows anything reads for a few hours and says great, I'll ask a question. At times that's good, I suppose, depending on the question? At times the rediculouis attitudes of newbeis flare and that is really making me sic to even to lurk.
The discussions that go on in this, and other forums are for the most part way above many. They should not feel like they are entiteled to an answer to their, let's say, NewB question within an hour of membership. But, they do? No matter what thread they ask it in. Down the raod there is all this, we should organize all this stuff. The fact of the matter is, it was organized, but all you NewBeez can't grasp it, or don't read enough, you think it's a CB radio or a chat room or Twitter or are just plain spoiled brats and think the world(the internet I suppose) is how you want it, or your gonna make it that way...
I spent quite a bit of time thinking about several posts lately in this thread, and a few other F5 related ones, for the benifit of the Newbeis. And, this confusion is still going on. The problem is, plain and simple, they all want the proverbial silver platter answer? Ain't happenin kiddies. Not even from N.P. Sorry if your an old fart like me but, most of them youngons don't give a ***t.
Don't complain when someone say's go read this or that book! Or even one of N.P.s articles. If you don't, sorry. I went to school to learn electronic stuff, I worked in the audio bis during school, I work now in the bisiness that gives you the computer to sit on your lazy butt and complain. I work with people like you with so called educations, you who have positions above me but are no more experienced than anyone else. But, your so called education and gung ho, get it done at all costs attitude, like so called managers, directors, exective bla, bla, while people like me do all your work, right. Your kissing the wrong butts. You can't learn this in school yet! They think on another level and they don't see this bisiness as a profit margin. This industry sells on another level or you would not be here!
Let me just tell all you newbies what you need to do. Take the advice of many, I'm not saying I'm one but don't rule me out. Go read everything on N.P.'s sites! All 3 of 'em are not as long as this thread! Or the F5 thread! If you don't understand read it again! I'm not kidding. If you think it's easier than that, don't argu with me, go somewhere else. It's not easier than that! lf I'm wrong, why aren't there 100's of N.P.'s out there? You can't start in the middle of these F5 threads and know what your talking about without a little experience. If you don't have it, at least go back to the begining and read. Then ask questions, or reread. all the confusion is unfounded. People are asking the same questions about stuff that was explaned pages ago, over and over? And by N.P years ago!
Many, many, qualified, consederit, helpfull people have been here and left, for I suppose what I just said. You have lost the benifit of their experience due to your impatience, attitude and lack of effort!
We are not all jumping in, because we are seasoned and we know better. Someone who barely knows anything reads for a few hours and says great, I'll ask a question. At times that's good, I suppose, depending on the question? At times the rediculouis attitudes of newbeis flare and that is really making me sic to even to lurk.The discussions that go on in this, and other forums are for the most part way above many. They should not feel like they are entiteled to an answer to their, let's say, NewB question within an hour of membership. But, they do? No matter what thread they ask it in. Down the raod there is all this, we should organize all this stuff. The fact of the matter is, it was organized, but all you NewBeez can't grasp it, or don't read enough, you think it's a CB radio or a chat room or Twitter or are just plain spoiled brats and think the world(the internet I suppose) is how you want it, or your gonna make it that way...
I spent quite a bit of time thinking about several posts lately in this thread, and a few other F5 related ones, for the benifit of the Newbeis. And, this confusion is still going on. The problem is, plain and simple, they all want the proverbial silver platter answer? Ain't happenin kiddies. Not even from N.P. Sorry if your an old fart like me but, most of them youngons don't give a ***t.
Don't complain when someone say's go read this or that book! Or even one of N.P.s articles. If you don't, sorry. I went to school to learn electronic stuff, I worked in the audio bis during school, I work now in the bisiness that gives you the computer to sit on your lazy butt and complain. I work with people like you with so called educations, you who have positions above me but are no more experienced than anyone else. But, your so called education and gung ho, get it done at all costs attitude, like so called managers, directors, exective bla, bla, while people like me do all your work, right. Your kissing the wrong butts. You can't learn this in school yet! They think on another level and they don't see this bisiness as a profit margin. This industry sells on another level or you would not be here!
Let me just tell all you newbies what you need to do. Take the advice of many, I'm not saying I'm one but don't rule me out. Go read everything on N.P.'s sites! All 3 of 'em are not as long as this thread! Or the F5 thread! If you don't understand read it again! I'm not kidding. If you think it's easier than that, don't argu with me, go somewhere else. It's not easier than that! lf I'm wrong, why aren't there 100's of N.P.'s out there? You can't start in the middle of these F5 threads and know what your talking about without a little experience. If you don't have it, at least go back to the begining and read. Then ask questions, or reread. all the confusion is unfounded. People are asking the same questions about stuff that was explaned pages ago, over and over? And by N.P years ago!
Many, many, qualified, consederit, helpfull people have been here and left, for I suppose what I just said. You have lost the benifit of their experience due to your impatience, attitude and lack of effort!
Oh Sh*t. I just read my post again, and realised how that could be interpreted. Sorry flg if I offended you. That was not directed at you at all. It was directed at everyone including myself.
I am tired of all the arguments, when most of the time there is nothing to argue about.
I am not sure how much of your message was directed at me, but I am definitely not one of those smart people. I am proud to say I am dumb (just ask my wife, she will tell you).
I try very hard to help people as much as I can, and actually spend quite a bit of time doing that (eg simulation work etc).
I love everyone here.
Sometimes I get frustrated and don't understand why people always have to put each other down. What is gained from that?
Things are not going to change I know.
Just want to make sure people don't think I was specifically targeting any individual. "It's the vibe of the thing your Honour" - The Castle
I am tired of all the arguments, when most of the time there is nothing to argue about.
I am not sure how much of your message was directed at me, but I am definitely not one of those smart people. I am proud to say I am dumb (just ask my wife, she will tell you).
I try very hard to help people as much as I can, and actually spend quite a bit of time doing that (eg simulation work etc).
I love everyone here.
Sometimes I get frustrated and don't understand why people always have to put each other down. What is gained from that?
Things are not going to change I know.
Just want to make sure people don't think I was specifically targeting any individual. "It's the vibe of the thing your Honour" - The Castle
I never intended to put you down.
I was posting in the same direction as you did. Agreeing what you said and
precising the rail voltage for those who could have been confused.
"two pairs" was a thinking loud comment approving your statement.
Your posts are appreciated, take it easy, life is beautiful
you did very clearly state assuming no losses
but there should be no need for assuming, when we know the facts
hey, just joking
I think it would be fair to say that these kind of 'explaining' can be tedious and hard to get 100% perfect
besides, if everyone gets scared of making mistakes
who will post then 
but there should be no need for assuming, when we know the facts
hey, just joking
I think it would be fair to say that these kind of 'explaining' can be tedious and hard to get 100% perfect
besides, if everyone gets scared of making mistakes
who will post then BJTs and mosFETs behave slightly different with regard to bias requirement.
Both types can be operated in ClassB, ClassAB and ClassA.
ClassB is when all output devices do not pass bias current at quiescent condition.
ClasssA is when all devices take an active role in controlling the output current all the time by never being allowed to go into an inactive state at any time, i.e. they must not be artificial current sources for a small period of the waveform.
ClassAB is that bias state in between where half the output devices do not play an active role in controlling output current during the whole waveform.
It is in ClassAB that BJTs and mosFETs differ. Since the F5 is based on mosFETs for output devices, I'll start there.
at a tiny bias current where all devices are passing a small bias current at quiescent condition the amp suffers crossover distortion when the output current crosses over from upper to lower or vice versa, another way of stating that is that output current is near twice the bias current (total bias for all upper devices or for all lower devices in the output stage). Note near in the definition. When the output current is well below twice the bias current the output stage is operating in ClassA. When the output current is well above twice the bias current the output stage upper devices work alone in controlling the output and later in the waveform the lower devices work alone in controlling the waveform.
MosFETs deliver better performance with regard to output distortion, the more bias current they pass (Pass has a paper on this).
One can increase the bias current such that the devices operate in ClassA for much more of the required output signal. This can be increased all the way to full ClassA. The performance keeping on improving.
The BJT output stage is quite different when operating in ClassAB mode. Again when output current is near twice the bias current the amp suffers from crossover distortion.
When output current is well below twice the bias current it operates in ClassA. These two operational modes are very similar to mosFETs.
When the BJT delivers more current than twice the bias current, the output distortion increases. The BJTs require an optimal bias current (based on voltage) to minimise the crossover distortion.
For our F5 using mosFETs, the more bias current for each device, the better.
The more total bias current, the more ClassA output before moving into ClassAB mode.
Does that help your osmosis?
BTW,
Borbely agrees.
He states that the minimum total bis current for his mosFET output stages should be 500mA. He does not state a maximum.
He also states that the minimum device bias current should be 100mA, again he does not state a maximum.
Both types can be operated in ClassB, ClassAB and ClassA.
ClassB is when all output devices do not pass bias current at quiescent condition.
ClasssA is when all devices take an active role in controlling the output current all the time by never being allowed to go into an inactive state at any time, i.e. they must not be artificial current sources for a small period of the waveform.
ClassAB is that bias state in between where half the output devices do not play an active role in controlling output current during the whole waveform.
It is in ClassAB that BJTs and mosFETs differ. Since the F5 is based on mosFETs for output devices, I'll start there.
at a tiny bias current where all devices are passing a small bias current at quiescent condition the amp suffers crossover distortion when the output current crosses over from upper to lower or vice versa, another way of stating that is that output current is near twice the bias current (total bias for all upper devices or for all lower devices in the output stage). Note near in the definition. When the output current is well below twice the bias current the output stage is operating in ClassA. When the output current is well above twice the bias current the output stage upper devices work alone in controlling the output and later in the waveform the lower devices work alone in controlling the waveform.
MosFETs deliver better performance with regard to output distortion, the more bias current they pass (Pass has a paper on this).
One can increase the bias current such that the devices operate in ClassA for much more of the required output signal. This can be increased all the way to full ClassA. The performance keeping on improving.
The BJT output stage is quite different when operating in ClassAB mode. Again when output current is near twice the bias current the amp suffers from crossover distortion.
When output current is well below twice the bias current it operates in ClassA. These two operational modes are very similar to mosFETs.
When the BJT delivers more current than twice the bias current, the output distortion increases. The BJTs require an optimal bias current (based on voltage) to minimise the crossover distortion.
For our F5 using mosFETs, the more bias current for each device, the better.
The more total bias current, the more ClassA output before moving into ClassAB mode.
Does that help your osmosis?
BTW,
Borbely agrees.
He states that the minimum total bis current for his mosFET output stages should be 500mA. He does not state a maximum.
He also states that the minimum device bias current should be 100mA, again he does not state a maximum.
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Nice summary Andrew.
Just want to add to this. Keep in mind the sweet spot will be different for each individual, depending on what speakers one has, how loud they listen to music and how much heatsinking they have.
eg It would be better off having less bias and more voltage swing if it means not voltage clipping the amp. ie I would rather go into class AB than voltage clip the amp.
If people think about what their requirements actually are and not just blindly copy a commercial design then it should be possible to make something that sounds absolutely fantastic.
If you have the heatsinking then just go nuts. I always bias my amps as high as my heatsinks (and output devices) will tolerate.
I know I don't exceed 18V peaks into my speakers but I still like to allow another 10V on top of that (28V - that's 32V including losses) and then I bias the hell out of the thing.
Just want to add to this. Keep in mind the sweet spot will be different for each individual, depending on what speakers one has, how loud they listen to music and how much heatsinking they have.
eg It would be better off having less bias and more voltage swing if it means not voltage clipping the amp. ie I would rather go into class AB than voltage clip the amp.
If people think about what their requirements actually are and not just blindly copy a commercial design then it should be possible to make something that sounds absolutely fantastic.
If you have the heatsinking then just go nuts. I always bias my amps as high as my heatsinks (and output devices) will tolerate.
I know I don't exceed 18V peaks into my speakers but I still like to allow another 10V on top of that (28V - that's 32V including losses
) and then I bias the hell out of the thing.
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I never intended to put you down.
I was posting in the same direction as you did. Agreeing what you said and
precising the rail voltage for those who could have been confused.
"two pairs" was a thinking loud comment approving your statement.
Your posts are appreciated, take it easy, life is beautiful
The camel's back has now been repaired and is in working order.
No worries mate.
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