Driver to drive?

[Kevin Aylward]

Chronic Philharmonic wrote:

"Eeyore" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:48D26873.19BC70AA@hotmail.com...


Arny Krueger wrote:

hahn.alan@gmail.com> wrote
RichD wrote:
Who do MOSFET sound better than bipolar, as an audio amp
output driver?

MOSFETS HAVE WIDER BANDWIDTH ,less phase shift , lower
odd harmonic distortin. on and on.

Not in any relevant way for audio power amps.

The first two are highly relevevant in ANY circuit using NFB. Basic
stability criteria.

Only if the bandwidth and the phase margins are small relative to the
target audio bandwidth, which is unlikely.

Ahmmmm....

Lets say we are after a 50khz closed loop BW, i.e. so that there is
negligible loss at 20khz. Now suppose we are after silly distortion levels,
say , 0.005% at 20Khz. Typically this means large amounts of feedback, say a
minimum of 40db at 20khz, maybe up to 60db even. This means that we need
say, a loop unity gain bandwidth of say 5Mhz min. Now, if the Ft of a big,
high voltage high current, bipolar was say 50Mhz, which is a tad on the fast
side, its current gain would have dropped to 10, which aint so great.
Furthermore, it would be really pushing a 50Mhz ft transistor to get an
overall stable loop at 5Mhz., not forgetting that there will already be, by
design, a dominant pole rolloff, prior to the output stage.

Lets do some sums:

Cin of a bipolar ~= gm/2.pi.ft X re/RL, in emiter follower mode, i.e. Cin =
1/(2.pi.ft.RL)

For a 50Mhz bipolor this would be 800pf. at 4 ohms.

A mosfet, would be Cin ~= Cgs/(gm.RL), which at typically 1A/V and 600p,
would be Cin=125pf.

So, despite the much larger gm of a bipolar to back off its inherent large
Cbe in source follower mode, they still typically need much more high
frequency drive than mosfets. Furthermore, without additional buffering,
this larger capacitance kills the h.f gain of the class a main gain stage,
as already mentioned by Graham. Indeed, in the early 80s, such 50Mhz devices
were made from unobtainium.

There are a lot of other details, but I really don't have the time to go
into any more detailed technical design at the moment.

So... try putting full on voltage on a mosfet without a heatsink for a
while, then try that with a bipolar!.

And hopefully I haven't made any errors in my calcs;-)

Kevin Aylward
http://www.kevinaylward.co.uk/ee/index.html

 

[Kevin Aylward]

Eeyore wrote:

Kevin Aylward wrote:

Trevor Wilson wrote:
"RichD" wrote

Who do MOSFET sound better than bipolar, as an audio amp output
driver?

**Non-sequitur. If you're saying that MOSFET outputs sound better,
they don't.

As a device, operating at typical bias currents (say) 10-50mA,
MOSFETs exhibit VASTLY more THD than BJTs. Only when bias currents
are elevated (around 0.5A - 1A) do MOSFETs exhibit THD
characteristics which are almost as good as BJTs.

MOSFETs are very tough, have an exceptional ability to deliver high
power, high frequency audio (and RF), but distortion is very high.
They require lots of Global NFB in order to operate linearly.

MOSFETs do not sound better than BJTs. At best, they can sound as
good. All things being equal.

Ahmm.... welll....here we go...

Well, I like mosfet outputs because they are easier to design with,
imo. Bipolars, often need an equivelent of 3 stage darlingtons. This
makes it a tad harder to stabilse the feedback loop because of each
stage pole.

Basically, you only need about 6 low current transistors, or so, to
achieve silly distortion and bandwidth figures, with mosfets.

As far as "sounds better", that's all moot. Any competently designed
amp should have thd, imd below audibility.

Seems to be a few that miss that though. Esp those Chinese copies of
copies.


Anyone that claims that a general purpose PA amp, sounds bad or not
good, if it has thd and imd < 0.005% and slew rates of 100V/us, is
pretty much delusional. Roll on the Ł200 oxygen free mains cable I
say....

Why stop at Ł200 ? Oh !
http://www.asa.org.uk/asa/adjudications/Public/TF_ADJ_44177.htm

Kevin, you'd be just the guy to do a harmonic analysis of the
distortion spectrum of a properly biased bipolar vs lateral mosfet
amp wouldn't you ? Any chance ?

It has just occurred to me, that you probably live quite close to me. I
live in Stevenage now, just a tad away from the old Luton hunting grounds. I
would say a joint visit to the pub for some Guinness might not go amiss.

Oh.. check out my current venture. Available for
bookings...www.blonddee.co.uk


Kevin Aylward
www.anasoft.co.uk
SuperSpice

 

[Phil Allison]

"MooseFET"
Vladimir Vassilevsky

1) With FETs, it is simpler to control bias current, because of the
negative dependency from the temperature. That simplifies the life.

Beware: Mosfets like the STW55NM60 have a decreasing threshold
voltage for increasing temperature.


** Every switching MOSFET made has a negative gate threshold voltage tempco.

Equates to a VERY positive drain current tempco.

Many times more severe than a BJT.




...... Phil

 

[Kevin Aylward]

RichD wrote:

On Sep 18, "Kevin Aylward" <kaExtractT...@kevinaylward.co.uk> wrote:
Who do MOSFET sound better than bipolar, as an audio amp output
driver?

**Non-sequitur. If you're saying that MOSFET outputs sound better,
they don't.

As a device, operating at typical bias currents (say) 10-50mA,
MOSFETs exhibit VASTLY more THD than BJTs. Only when bias currents
are elevated (around 0.5A - 1A) do MOSFETs exhibit THD
characteristics which are almost as good as BJTs.

MOSFETs are very tough, have an exceptional ability to deliver high
power, high frequency audio (and RF), but distortion is very high.
They require lots of Global NFB in order to operate linearly.

MOSFETs do not sound better than BJTs. At best, they can sound as
good. All things being equal.

Well, I like mosfet outputs because they are easier to design with,
imo. Bipolars, often need an equivelent of 3 stage darlingtons. This
makes it a tad harder to stabilse the feedback loop because of each
stage pole.

Basically, you only need about 6 low current transistors, or so, to
achieve silly distortion and bandwidth figures, with mosfets.

As far as "sounds better", that's all moot. Any competently designed
amp should have thd, imd below audibility.

Anyone that claims that a general purpose PA amp, sounds bad or not
good, if it has thd and imd < 0.005% and slew rates of 100V/us, is
pretty much delusional.

Do you have any experience designing audio amps?

er... yes...e.g.

http://www.studiomaster.com/1984%20-%201986.htm

"This was the amplifier pro sound companies were waiting for; many buy up to
100 units. "

Which did you use?

Right now I use a few, one of which is a studiomaster AX2500 (750+750),
which I did not design. I also have a Behringer 1280S mixer/amp, and a
Carlsbro (600+600) PA..and a.etc...etc...

Kevin Aylward
www.anasoft.co.uk
SuperSpice

 

[Kevin Aylward]

Eeyore wrote:

Kevin Aylward wrote:

Anyone that claims that a general purpose PA amp, sounds bad or not
good, if it has thd and imd < 0.005% and slew rates of 100V/us, is
pretty much delusional. Roll on the Ł200 oxygen free mains cable I
say....

Why stop at Ł200 ? Oh !
http://www.asa.org.uk/asa/adjudications/Public/TF_ADJ_44177.htm

This link seems to be bad. I did find this though

http://divinecables.co.uk/mains-power-cable/19/kemp-hi-power-cable#

All I can say, is that I am still stunned..and shocked...shocked and
stunned...all I said was that I was taller than Jesus, not that I was bigger
than Jesus...


Kevin Aylward

 

[Guy Macon]

George Herold wrote:

Dirk Bruere at NeoPax wrote:

John Larkin wrote:

Ground both ends, hard, to the equipment chassis. Why would you want
huge common-mode spikes on your data? Why bother with a shield if it's
going to have nasty potentials on it relative to the signals?

You might also have some big currents flowing in the shield if the
"ground" at each end is a different voltage.

You might also have some big currents flowing in the shield if the
"ground" at each end is a different voltage.

Which is why you sometimes "get by" by putting some resistance in one
side of the ground connection. I see no reason to put 100 ohms at
both end though.

The reasoning behind the resistor on each end is that cable runs
sometimes get worn insulation and end up with the shield connected
to earth ground somewhere in the middle of the run. The resistor
on each end limits the current through the shield in such cases.


--
Guy Macon
<http://www.GuyMacon.com/>

 

[Kevin Aylward]

Eeyore wrote:

Kevin Aylward wrote:

Eeyore wrote:
Kevin Aylward wrote:
Trevor Wilson wrote:
"RichD" wrote

Who do MOSFET sound better than bipolar, as an audio amp output
driver?

**Non-sequitur. If you're saying that MOSFET outputs sound better,
they don't.

As a device, operating at typical bias currents (say) 10-50mA,
MOSFETs exhibit VASTLY more THD than BJTs. Only when bias currents
are elevated (around 0.5A - 1A) do MOSFETs exhibit THD
characteristics which are almost as good as BJTs.

MOSFETs are very tough, have an exceptional ability to deliver
high power, high frequency audio (and RF), but distortion is very
high. They require lots of Global NFB in order to operate
linearly.

MOSFETs do not sound better than BJTs. At best, they can sound as
good. All things being equal.

Ahmm.... welll....here we go...

Well, I like mosfet outputs because they are easier to design with,
imo. Bipolars, often need an equivelent of 3 stage darlingtons.
This makes it a tad harder to stabilse the feedback loop because
of each stage pole.

Basically, you only need about 6 low current transistors, or so, to
achieve silly distortion and bandwidth figures, with mosfets.

As far as "sounds better", that's all moot. Any competently
designed amp should have thd, imd below audibility.

Seems to be a few that miss that though. Esp those Chinese copies of
copies.

Anyone that claims that a general purpose PA amp, sounds bad or not
good, if it has thd and imd < 0.005% and slew rates of 100V/us, is
pretty much delusional. Roll on the Ł200 oxygen free mains cable I
say....

Why stop at Ł200 ? Oh !
http://www.asa.org.uk/asa/adjudications/Public/TF_ADJ_44177.htm

Kevin, you'd be just the guy to do a harmonic analysis of the
distortion spectrum of a properly biased bipolar vs lateral mosfet
amp wouldn't you ? Any chance ?

It has just occurred to me, that you probably live quite close to
me. I live in Stevenage now, just a tad away from the old Luton
hunting grounds. I would say a joint visit to the pub for some
Guinness might not go amiss.

Sounds ok to me. I'm in St Albans.

Yeah, just down the road...16.7M according to the AA. Although with a
suggested time of 20mins, obviously, the AA don't know how to drive...

Will contact you off group.

Look foward to it. My phone # is on my websites.

Oh.. check out my current venture. Available for
bookings...www.blonddee.co.uk

OK will do. I know someone who might even book you.

Oh.. nice...

Kevin Aylward

 

[Kevin Aylward]

Eeyore wrote:

Kevin Aylward wrote:

Eeyore wrote:
Kevin Aylward wrote:

Anyone that claims that a general purpose PA amp, sounds bad or not
good, if it has thd and imd < 0.005% and slew rates of 100V/us, is
pretty much delusional. Roll on the Ł200 oxygen free mains cable I
say....

Why stop at Ł200 ? Oh !
http://www.asa.org.uk/asa/adjudications/Public/TF_ADJ_44177.htm

This link seems to be bad. I did find this though

Works here.

worked now.

http://divinecables.co.uk/mains-power-cable/19/kemp-hi-power-cable#

All I can say, is that I am still stunned..and shocked...shocked and
stunned...all I said was that I was taller than Jesus, not that I
was bigger than Jesus...

I'd like to start a movement to have all these liars and fraudsters
shut down.

Indeed. If I had actually said that I was bigger than Jesus, I would have
said so...

As you may have noticed from visiting churches, the average height a while
back, was a lot smaller...

Kevin Aylward

 

[Kevin Aylward]

Eeyore wrote:

John Larkin wrote:

Eeyore wrote:
John Larkin wrote:
Eeyore wrote:

Learn something about LATERAL mosfets that were designed for
audio. I've already given part number and links to data sheets.

That doesn't really matter. The transfer function only needs to be
continuous so that you can close a loop around it, and the fet
needs to be able to stand the peak power dissipation. That can
easily be done with vertical "switching" type fets. A modern FLOOD
architecture [1] works great with most any kind of fet. Lots of
things have changed in the last few decades.

John

[1] Of course you've never heard the term before. I just invented
it.

Fine. Can you elaborate some more on it ? Laterals have some truly
lovely features for audio. The only downside being a slightly
highish Ron. Not really a problem when (as I have) used as many as
6 in parallel (12 mosfets per channel / 24 per amp). They also
match beautifully with no need for source balance resistors (so
some of the Ron loss 'goes away').


An opamp per fet, closing a local loop, feedback from the fet source,
makes each fet look like a perfect unity-gain, fast, zero-offset
device.

Interesting idea. I'll have to chew that one over. I can see possible
problems fron op-amp output overshoot.

I have a simple embodiment of that concept here, done a while ago, in
virtual land;-)

http://www.kevinaylward.co.uk/ee/circuits/VeryLowDistortionAmp2.jpg

Its a push/pull gain loop around the output devices, forcing them to be
unity gain followers.

You can get lower distortion, at the expense of speed, because you have to
compensate earlier.

Common mode feedback at the second stage, allows for enormous dc/lf gain.
cascodes to allow the use of fast small transistors to do all the main work.
Emitter follower buffer to reduce the current swing in the input pair, as
per doug self. Spice says it should be in the < 0.0001% , 20Khz range,
maybe...

Kevin Aylward

 

[Kevin Aylward]

Joerg wrote:

Hello Folks,

Title says it all. LTSpice constantly grinds on the hard drive,
storing raw data and what not. In my case it's all on a LAN drive so
this is especially annoying. Plus that will wear it out over time,
not good at all. With a 2GB RAM machine there is no reason whatsoever
to store 20M of raw data on every single run.

How can I stop this?

well. I remember years ago being able to setup a ram dive on, I belive, an
atari. No doubt something like this will exist for windows. i.e the program
thinks it writting to say k:\ drive, but it aint. I suggest a web search

Kevin Aylward
www.anasoft.co.uk

 

[Kevin Aylward]

Jan Panteltje wrote:

On a sunny day (Fri, 19 Sep 2008 18:10:20 +0100) it happened Eeyore
rabbitsfriendsandrelations@hotmail.com> wrote in
48D3DCFC.622BDEE3@hotmail.com>:

An opamp per fet, closing a local loop, feedback from the fet
source, makes each fet look like a perfect unity-gain, fast,
zero-offset device.

Interesting idea. I'll have to chew that one over. I can see
possible problems fron op-amp output overshoot.

If you loo kat the TDA9274 datahseet (the ST DMOS chip), then in the
blockdiagram on page 2 you will see this is exactly what is done with
the lower output MOSFET, combined with opamp makes unity gain.
The top is already a source followwr.
The over current protection same thing, opamps.
It is likely this what makes the Boucherot network not needed.

I doubt it. I haven't seen the data sheet, but it is not usual to be able to
stabilise an amp with what I believe you are describing here.

Consider one amp feeding the other, both running open loop, with overall
feedback, to the 1st. Now consider the case where the second amp is
configured with local feedback, to make it a unity buffer, following the 1st
amp. Naively , one might argue that the 2nd stage now has a wider bandwidth,
due to feedback, such that the "new " system might be stable, i.e. one main
rolloff due to the 1st amp. However, in realty, topologically, nothing
changes. The determine the stability of the system, one needs to break the
loop at a point that breaks *all* feedback paths at once. This point will be
the point directly at the output of the 2nd amp. when this is done, it is
clear that the stabiliy is still due to the total loop gain of both amops
cascaded.

Excepting for the special cases, e.g. , where feedback is used to neutralise
r.f amps, feedback in general, cannot be used to widen bandwidth, if the
purpose of that wider bandwidth is to achieve stability, in this type of
arrangement

To wit, There is no such thing as a free lunch...

Kevin Aylward

www.superspice.co.uk

 

[Kevin Aylward]

John Larkin wrote:

On Fri, 19 Sep 2008 18:10:20 +0100, Eeyore
rabbitsfriendsandrelations@hotmail.com> wrote:



John Larkin wrote:

Eeyore wrote:
John Larkin wrote:
Eeyore wrote:

Learn something about LATERAL mosfets that were designed for
audio. I've already given part number and links to data sheets.

That doesn't really matter. The transfer function only needs to be
continuous so that you can close a loop around it, and the fet
needs to be able to stand the peak power dissipation. That can
easily be done with vertical "switching" type fets. A modern
FLOOD architecture [1] works great with most any kind of fet.
Lots of things have changed in the last few decades.

John

[1] Of course you've never heard the term before. I just invented
it.

Fine. Can you elaborate some more on it ? Laterals have some truly
lovely features for audio. The only downside being a slightly
highish Ron. Not really a problem when (as I have) used as many as
6 in parallel (12 mosfets per channel / 24 per amp). They also
match beautifully with no need for source balance resistors (so
some of the Ron loss 'goes away').


An opamp per fet, closing a local loop, feedback from the fet
source, makes each fet look like a perfect unity-gain, fast,
zero-offset device.

Interesting idea. I'll have to chew that one over. I can see
possible problems fron op-amp output overshoot.


It needs a little loop tweaking, roughly....


V+
|\ |
-----------| + |
| d
| out-------+------Rg--------g
| | s
+------| - | |
| |/ Cf |
| | |
+--------------------+------Rf---------+
|
|
Rs
|
|
+------------- output rail


and an opamp that can slam the gate hard enough, not a big problem
nowadays. That whole thing becomes one ideal pseudo-fet of many. Rs
can be small, and the quiescent bias voltage can be small, because the
opamp offset voltage can be tiny. The fets share the load exactly, and
the standing bias current can be designed in, exactly, with no
adjustments.

The driver stage sees only opamps, so doesn't have to work very hard.

However....there are some issues with using whole op-amps, rather than
discrete transistors as I have in the noted circuit in my other post. You
may need 200V+ ratings, and a very fast one at that!!!


Kevin Aylward
kevin@kevinaylward.co.uk
www.kevinaylward.co.uk

 

[Guy Macon]

mpm wrote:

Still, it seems once or twice a year the theatrical lighting
controller at our Church gets absolutely hammered with lightning.

Intall a good set of lighting rods -- you may only need one if
you have a steeple -- with a proper grounding line.

References:
http://www.lightningsafety.com/nlsi_lhm/lpts.html
http://www.inspect-ny.com/lightning/lightning.htm
http://en.wikipedia.org/wiki/Lightning_rod
http://www.lightningsafety.com/nlsi_lhm/Uman_Rakov.pdf


--
Guy Macon
<http://www.GuyMacon.com/>

 

[Jon Slaughter]

"Jim Thompson" <To-Email-Use-The-Envelope-Icon@My-Web-Site.com> wrote in
message news:gv98d4hjh1aisqbp8jlc6u6qsf1dps9kmq@4ax.com...

Father/daughter talk...

A young woman was about to finish her first year of college. Like so
many others her age, she considered herself to be a very liberal
Democrat, and among other liberal ideals, was very much in favor of
higher taxes to support more government programs, in other words,
redistribution of wealth.

She was deeply ashamed that her father was a rather staunch
Republican, a feeling she openly expressed.

Based on the lectures that she had participated in, and the occasional
chat with a professor, she felt that her father had for years harbored
an evil, selfish desire to keep what he thought should be his.

One day she was challenging her father on his opposition to higher
taxes on the rich and the need for more government programs.

The self-professed objectivity proclaimed by her professors had to be
the truth and she indicated so to her father.

He asked how she was doing in school.

Taken aback, she answered rather haughtily that she had a 4.0 GPA, and
let him know that it was tough to maintain, insisting that she was
taking a very difficult course load and was constantly studying, which
left her no time to go out and party like other people she knew.

She didn't even have time for a boyfriend, and didn't have time for
partying with friends because she spent all her time studying.

Her father listened and then asked, 'How is your friend Audrey doing?'

She replied, 'Audrey is barely getting by. All she takes are easy
classes, she never studies, and she barely has a 2.0 GPA. She is so
popular on campus; college for her is a blast. She's always invited to
all the parties and lots of times she doesn't even show up for her
classes because she's too hung over.'

Her wise father asked his daughter, 'Why don't you go to the Dean's
office and ask him to deduct 1.0 off your GPA and give it to your
friend who only has a 2.0. That way you will both have a 3.0 GPA and
certainly that would be a fair and equal distribution of GPA.'

The daughter, visibly shocked by her father's suggestion, angrily
fired back, That's insane!

How could that be fair???

I've worked really hard for my grades! I've invested a lot of time,
and a lot of hard work!

Audrey has done next to nothing toward her degree. She played while I
worked my tail off!'

The father sheepishly smiled, winked and said gently, 'Welcome to the
Republican party.'

I've never heard a better explanation of the difference between
Republican and Democrat. Nancy Pelosi's father should have had this
conversation with her.

================

It's too logical for someone with a 4.0 to understand! In fact the daughter
was just too damn ugly to do anything else but study! and only learned how
to memorize instead of actually think.

If anything, we should first take away from those that want to give. Since
the liberals are so eager to give up everyone's money(rather take) we should
start with taking from them. Now thats a true lesson!! 50% hike in taxes on
all liberals!!!

 

[Jon Slaughter]

The analogy doesn't work. In a "Republican" college, the top students
would be able to accumulate unlimited GPA points and use them in
bidding wars to get into the best and most popular courses, whose GPA
point return value would rise and fall with supply and demand.
Meanwhile, slower students would mostly be consigned to low-cost, dead-
end, low GPA point courses such as Introduction to Floor Polishing.
Only a tiny minority would actually ever graduate and they'd be able
to roll their surplus GPA points over to their children as hereditary
degrees.

--

Maybe those students who aren't at the top should spend a little more time
at the library instead of the pub?

 

[Jon Slaughter]

"Paul Hovnanian P.E." <paul@hovnanian.com> wrote in message
news:48D44F84.5446F736@hovnanian.com...

"J.A. Legris" wrote:

[snip]

The analogy doesn't work. In a "Republican" college, the top students
would be able to accumulate unlimited GPA points and use them in
bidding wars to get into the best and most popular courses, whose GPA
point return value would rise and fall with supply and demand.
Meanwhile, slower students would mostly be consigned to low-cost, dead-
end, low GPA point courses such as Introduction to Floor Polishing.
Only a tiny minority would actually ever graduate and they'd be able
to roll their surplus GPA points over to their children as hereditary
degrees.

They'd be able to buy the services of members of the football team to
follow them around and keep them from getting beaten up.

They'd also loan GPA to some of the poorer, but popular students who
they could eventually back as candidates for political offices. Then
they could call in the loans in the event one became president or
something like that.



But the main reason Jim's story doesn't make sense is that the father of
a 4.0 GPA student would certainly lecture his daughter about how doing
well in school was her way of honoring her ancestors back in
China/Japan/Korea/etc. A caucasian 4.0 student is too rare to make a
plausible story.

My guess is that it makes complete sense but you are just too smart to
understand. Since you believe in giving so much do you accept the 50% tax
hike on all liberals? Once you guys get your programs going and show us that
they are worth it we will then give in.

 

[Michael Press]

In article
<efd97854-f436-40a2-96f9-590a7235c435@i76g2000hsf.googlegroups.com>,
George Herold <ggherold@gmail.com> wrote:

On Sep 19, 11:38 am, Phil Hobbs
pcdhSpamMeSensel...@electrooptical.net> wrote:
George Herold wrote:

Thanks Phil,  I've been doing some with autocorrelation functions
lately (in relation to noise).  I was thinking you could define a
spacial correlation function.  Solids are highly spacially correlated,
gasses not at all and perhaps liquids have a short range
correlation.

Crystals have high spatial correlations over long distances, but
amorphous solids don't.  Even 2-D crystals e.g. graphene don't have long
range order, interestingly enough---you need 3 dimensions before the
sums of the random fluctuations remain bounded as x->infinity.

Crystals have high spatial correlations over long distances, but
amorphous solids don't .
Yeah and people are always telling me that glass can be thought of as
a liquid... but with a long relaxation time. Is the same true of all
amorphous solids?

Thinking of glass as a liquid predicts incorrectly.
One circumstance governing rate of flow of a liquid
is the radius of curvature at its boundary.
If glass flowed, glass knives would not keep their edge.
But microbiology laboratories all over the world use glass mircrotomes.

Look up glass transition temperature.

--
Michael Press

 

[Bob Eld]

"Jim Thompson" <To-Email-Use-The-Envelope-Icon@My-Web-Site.com> wrote in
message news:gv98d4hjh1aisqbp8jlc6u6qsf1dps9kmq@4ax.com...

Father/daughter talk...

A young woman was about to finish her first year of college. Like so
many others her age, she considered herself to be a very liberal
Democrat, and among other liberal ideals, was very much in favor of
higher taxes to support more government programs, in other words,
redistribution of wealth.

She was deeply ashamed that her father was a rather staunch
Republican, a feeling she openly expressed.

Based on the lectures that she had participated in, and the occasional
chat with a professor, she felt that her father had for years harbored
an evil, selfish desire to keep what he thought should be his.

One day she was challenging her father on his opposition to higher
taxes on the rich and the need for more government programs.

The self-professed objectivity proclaimed by her professors had to be
the truth and she indicated so to her father.
Snip.....

So tell us Mr. republican, How do you feel about the Bush Administration's
NATIONALIZATION of AIG and further appropriations of other troubled PRIVATE
institutions to the tune of maybe a TRILLION in tax payer money?

What? Have you republicans now decided to use Karl Marx's solution to the
problems in Capitalism. It seems your solution isn't much different than
what Hugo Chavez is doing.

And, you have the gall to not want health care for Americans because it is
Socialism. What phonies you are. You want to keep your money, fancy that!
Where the hell is that trillion going to come from?

We now have a European Socialization solution to a Capitalistic problem
because you jackasses can't manage an economy. What irony that it takes
socialism to fix America's problems.

Your republican greed and avarice is overwhelming. It's sad that your
refusal to accept a reasonable amount of taxation, regulation, control and
direction has now brought us to a socialized solution. How pathetic.

I hope your daughter like most young people today throws off this republican
yoke and helps elect a Democratic government like was done in 1932 when the
republicans also screwed the American economy. Some people never learn.

 

[Michael Press]

In article
<3402b74a-62c7-4048-b71f-acc9788b8889@l43g2000hsh.googlegroups.com>,
Benj <bjacoby@iwaynet.net> wrote:

On Sep 19, 9:49 pm, Michael Press <rub...@pacbell.net> wrote:

Thinking of glass as a liquid predicts incorrectly.
One circumstance governing rate of flow of a liquid
is the radius of curvature at its boundary.
If glass flowed, glass knives would not keep their edge.
But microbiology laboratories all over the world use glass mircrotomes.

Look up glass transition temperature.
So what is the glass transition temperature?

I suggested that you look it up. It is obvious that you
will not take my word for any of this.

The "flow" of glass is
well known. Glass tubing leaned into a corner for years will develop a
permanent bend. That still doesn't mean that it won't hold an edge
long enough to be useful in a microtome.

Those glass rods do not bend.
And if glass flowed, glass knives would not keep their edge.
Glass knives hundreds of years old have been discovered
with their edge. You are saying that a glass rod will sag,
and a hundred year old glass knife will keep its edge?

--
Michael Press

 

[Kevin Aylward]

Don Pearce wrote:

Kevin Aylward wrote:
Eeyore wrote:
John Larkin wrote:

Eeyore wrote:
John Larkin wrote:
Eeyore wrote:
Learn something about LATERAL mosfets that were designed for
audio. I've already given part number and links to data sheets.
That doesn't really matter. The transfer function only needs to
be continuous so that you can close a loop around it, and the fet
needs to be able to stand the peak power dissipation. That can
easily be done with vertical "switching" type fets. A modern
FLOOD architecture [1] works great with most any kind of fet.
Lots of things have changed in the last few decades.

John

[1] Of course you've never heard the term before. I just invented
it.
Fine. Can you elaborate some more on it ? Laterals have some truly
lovely features for audio. The only downside being a slightly
highish Ron. Not really a problem when (as I have) used as many as
6 in parallel (12 mosfets per channel / 24 per amp). They also
match beautifully with no need for source balance resistors (so
some of the Ron loss 'goes away').

An opamp per fet, closing a local loop, feedback from the fet
source, makes each fet look like a perfect unity-gain, fast,
zero-offset device.
Interesting idea. I'll have to chew that one over. I can see
possible problems fron op-amp output overshoot.

I have a simple embodiment of that concept here, done a while ago, in
virtual land;-)

http://www.kevinaylward.co.uk/ee/circuits/VeryLowDistortionAmp2.jpg

Its a push/pull gain loop around the output devices, forcing them to
be unity gain followers.

You can get lower distortion, at the expense of speed, because you
have to compensate earlier.

Common mode feedback at the second stage, allows for enormous dc/lf
gain. cascodes to allow the use of fast small transistors to do all
the main work. Emitter follower buffer to reduce the current swing
in the input pair, as per doug self. Spice says it should be in the
0.0001% , 20Khz range, maybe...

Kevin Aylward



Kevin - an interesting circuit, and I appreciate what you have done
with the output stage, but I'm still wondering why you didn't include
it within the global feedback loop - that could only have made it
better, lower output impedance, more load insensitive etc etc etc.

It is.!!!

I think the schematic is not as clear as it should be.. I have a zero volt
source near the output devices in the feedback circuit to calculate LG. The
overall loop feedback passes through this source!!!

Regards

Kevin Aylward
www.blonddee.co.uk
www.kevinaylward.co.uk