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What characterizes a powerFET for audio use?

N

N_Cook

Jan 1, 1970
0
Other than p channel in this case , same for BUZ901P nch
eg BUZ906P 200V, 8A ,datasheet says
"POWER MOSFETS FOR
AUDIO APPLICATIONS"
but also
"FEATURES ... (for use in)
HIGH SPEED SWITCHING ... "

Would a powerFET designed solely for high speed switching use and 125W
rating be derated in power handling terms to only 50W say for linear 10
Hz use. Or secondary oscillation liability if paralleled up devices? or
some other operational failing in audio use not found with smps say ?
 
P

Phil Allison

Jan 1, 1970
0
"Nutcase Kook" is a pig ignorant pommy ****

Other than p channel in this case, same for BUZ901P nch
eg BUZ906P 200V, 8A ,datasheet says
"POWER MOSFETS FOR
AUDIO APPLICATIONS"
but also
"FEATURES ... (for use in)
HIGH SPEED SWITCHING ... "


** The Semelab app note makes it pretty clear there is a HUGE difference
between "switching" and audio ( ie lateral) power mosfets.

http://products.semelab-tt.com/pdf/ApplicationNoteAlfet.pdf

Would a powerFET designed solely for high speed switching use and 125W
rating be derated in power handling terms to only 50W say for linear 10 Hz
use. Or secondary oscillation liability if paralleled up devices? or some
other operational failing in audio use not found with smps say ?

** Yawnnnnnnnnnnnnnnn....

More brainless, fucking TROLLING !!!!!!!

FOAD you vile pommy cunthead.



..... Phil
 
W

William Sommerwerck

Jan 1, 1970
0
"dave" wrote in message
"Figure of Merit" in pulsed applications vs "efficiency"
in linear applications.

Any (???) device can produce more peak power in pulsed mode than continuous,
because it spends less time in the region where it dissipates the most power.

RMS power is measured in heating ability versus DC.

There is no such thing (other than in a mathematical sense) as RMS power.
Voltage and current can have RMS (root-mean-square) values. Squaring voltage
and dividing by resistance, or squaring current and multiplying by resistance
produces the //average// power.
 
M

Maynard A. Philbrook Jr.

Jan 1, 1970
0
And FOM is used (by me) because the efficiency is above 100%.

Oh really? have you found some over unity energy somewhere?

Jamie
 
W

William Sommerwerck

Jan 1, 1970
0
"Jeff Liebermann" wrote in message
RMS power is quite real. A true-RMS voltmeter uses a pair of heating
elements and thermocouples to produce a measurement because it's
the best way to measure the equivalent voltage that would generate
the same amount of heat. There are versions that use other methods
but the thermocouple is generally the closest to the real heating value.

The heating value of a waveform is the average value of its power, NOT the RMS
value of its power.

Many years ago I sat down and calculated this for a sine wave. I assure you, a
sine wave's average power and its RMS power are not at all the same. RMS
applies ONLY to voltage and current.
 
P

Phil Allison

Jan 1, 1970
0
"dave the dickhead "
"Figure of Merit" in pulsed applications vs "efficiency" in linear
applications. RMS Power is measured in heating ability v DC.


** Yaaawnnnnnnn - more stupid fucking bullshit !!!!!!!!!!!!!!

One colossal fool asks an idiotic question and even BIGGER fools reply.



..... Phil
 
P

Phil Allison

Jan 1, 1970
0
"William Sommerwerck"
Many years ago I sat down and calculated this for a sine wave. I assure
you, a sine wave's average power and its RMS power are not at all the
same. RMS applies ONLY to voltage and current.

** But even a complete fool like Somerwanker should know that the term "RMS
power" is not meant literally.

It is NOT the RMS value of the instantaneous power level.

In the world of audio, it normally refers to a power measurement done using
the RMS value of a sine wave (or other wave if specified ) voltage delivered
into a known resistive load.

A simple bit of calculus shows that the RMS value of a sine wave to be half
the square root of two ( 0.7071) times its peak value.


..... Phil
 
M

Maynard A. Philbrook Jr.

Jan 1, 1970
0
RMS power is quite real. A true-RMS voltmeter uses a pair of heating
elements and thermocouples to produce a measurement because it's the
best way to measure the equivalent voltage that would generate the
same amount of heat. There are versions that use other methods but
the thermocouple is generally the closest to the real heating value.

I got into his long ago, and all the proclaimed experts came out of the
wood work to say I was wrong. RMS power ratings have been stuck on
equipment as long as I can remember.

Jamie
 
W

William Sommerwerck

Jan 1, 1970
0
Many years ago I sat down and calculated this for a sine wave. I assure
** But even a complete fool...

I can't be a complete fool, because on rare occasions you agree with me.
...like Sommerwerck should know that the term "RMS power" is not
meant literally.

He knows nothing of the sort. Just because people say "pressure" when they
mean "force", doesn't mean pressure and force are the same thing.

I see ads proclaiming that an amplifier delivers "125 watts RMS power". No, it
doesn't. There is a perfectly good term for that... "continuous average
power", or perhaps "continuous average sinewave power". This term has a
specific meaning, and it IS NOT the same as RMS power.
 
P

Phil Allison

Jan 1, 1970
0
"William Sommerwanker = IDIOT"
I can't be a complete fool,

** Yes you are and about to prove it yet again.

He knows nothing of the sort.

** Proof given

I see ads proclaiming that an amplifier delivers "125 watts RMS power".
No, it doesn't.


** " ... the term "RMS power" is not meant literally."

Cos it is not what the writer meant PLUS there is simply no such quantity
if you do.

FUCKWIT !!!!!!!!!!!!


..... Phil
 
P

Phil Allison

Jan 1, 1970
0
"Jeff Liebermann"
Ok, I yield to a higher authority. Heating power is average power:
<http://www.eznec.com/Amateur/RMS_Power.pdf>
However that doesn't stop nearly everyone from specifying RMS power.

** There is no such quantity as " RMS power " if you are so stupid as to
interpret the term literally.
So, why do people buy true-RMS voltmeters?

** To get " true RMS " volts of course.

If they don't measure anything useful,


** The RMS value of a voltage or current could hardly be more useful.

My god, you are SOOOOOO illiterate and SOOOOO retarded.




.... Phil
 
P

Phil Allison

Jan 1, 1970
0
"Jeff Liebermann"
Which term should be interpreted non-literally?


** The term " RMS power " of course -

you fucking BLIND nut case ASSHOLE !!!!!!!!!!!!
----------------------------------------------------------

Very good. But since there doesn't seem to be any correlation with
heating power (despite using a thermocouple to do the measuring) and
RMS volts or watts,

** Quite wrong - there is a very close connection.
what does the meter indication on a true RMS
voltmeter actually mean? Or is it just a mathematical abstraction?

** RMS voltage or current value = the DC equivalent value.

So the DC power formulas: " I squared R " and " V squared / R "
still apply in power calculations using AC voltages & currents.
---------------------------------------------------------------------------



** The RMS value of a voltage or current could hardly be more useful.

My god, you are SOOOOOO illiterate and SOOOOO retarded.
Very perceptive and partly true.


** It's completely true.

You are the stupidest, most retarded, constantly lying fuckwit on the NG.

Get cancer and fucking DIE !



..... Phil
 
W

William Sommerwerck

Jan 1, 1970
0
"Jeff Liebermann" wrote in message
OK, I yield to a higher authority. Heating power is average power:
<http://www.eznec.com/Amateur/RMS_Power.pdf>
However that doesn't stop nearly everyone from specifying
RMS power.

Unfortunately, no.

So, why do people buy true-RMS voltmeters? If they don't measure
anything useful, why bother?

A fair question. Apparently, there was a time when AC power had a significant
percentage of harmonics (perhaps it still does), and engineers wanted to know
its "true" heating effect.
 
W

William Sommerwerck

Jan 1, 1970
0
"Jeff Liebermann" wrote in message

<http://www.eznec.com/Amateur/RMS_Power.pdf>
On Pg 6 it says:
"The RMS value of power is not the equivalent heating power and,
in fact, it doesn't represent any useful physical quantity."
and:
"The RMS power is different than the average power, and therefore
isn’t the equivalent heating power. In fact, the RMS value of the
power doesn’t represent anything useful."
It would seem that the author finds average power different from,
more useful than, and closer to heating power. Perhaps we should
change the name from "true-RMS voltmeter" to "true heating average
voltmeter"?

Jeff, you're misreading this. The author is saying //exactly// what I said.
(It's unfortunate he doesn't use a sine wave for his example, but the math
would then require integral calculus.)

Average power /is/ the heating power. (The rationale is that a resistor's
temperature is determined by the average power applied to it.) When we know
the RMS value of any repetitive waveform, we can compute its heating power by
squaring that voltage (current) and dividing (multiplying) by the resistor's
value.

Voltmeters (of all sorts) are usually calibrated to show the RMS value //of a
sine wave//. If the waveform differs, the value shown is wrong. One of the
advantages of a true-RMS meter is that all readings are "equivalent" in an
easily-comprehended way, regardless of the waveform -- even if that
"equivalency" has little practical usefulness. (If you want to know the
details of a waveform, you use a 'scope.)

I remember a Popular Electronics quiz with questions about how a voltmeter (at
that time, a moving-coil device) would read, depending on the waveform
supplied. A key point was that the deflection was proportional to the average
current flowing through the coil, but the meter was usually calibrated for the
RMS value of a sinewave.
 
W

Wond

Jan 1, 1970
0
<http://www.eznec.com/Amateur/RMS_Power.pdf> On Pg 6 it says:
"The RMS value of power is not the equivalent heating power and, in
fact, it doesn't represent any useful physical quantity."
and:
"The RMS power is different than the average power, and therefore
isnÂ’t the equivalent heating power. In fact, the RMS value of the
power doesnÂ’t represent anything useful."

It would seem that the author finds average power different from, more
useful than, and closer to heating power. Perhaps we should change the
name from "true-RMS voltmeter" to "true heating average voltmeter"?

"So it is written, so it shall be."
(Ramses in the CB DeMille version of the 10 Commandments).
(snipped)
ISTR it used to be a DC equivalent thing, ie, you need 6Vrms ac to
operate a 6VDC light bulb at spec.
I think Leak confused the issue when he branded those wonderful
audio amplifiers "RMS", thus putting the term in the realm of marketting.
 
W

William Sommerwerck

Jan 1, 1970
0
"dave" wrote in message
Why do you keep quoting notes from Llewelen? He wrote a modeling
program for wire antennas. We are talking about FETs.

Who is Llewelen?

I think AVG = RMS only if waveform is pure sinewave. Otherwise,
you must use calorimeter or thermocouple to find true RMS.

RMS and average are the same only for square waves. True RMS can be computed
by analog circuits, one of which made its way in dbx devices.
 
W

William Sommerwerck

Jan 1, 1970
0
"dave" wrote in message
The question was why is audio power spec is half that of DC on/off
capability. It is because the device stays on all the time and because the
audio waveform causes more heating. Worry about the labels
and fight all you want.

Exactly.
 
P

Phil Allison

Jan 1, 1970
0
"William Sommerwanker is a bullshitting ass."
A fair question.


** Wrong - it's a fuckwit question.
Apparently, there was a time when AC power had a significant percentage of
harmonics (perhaps it still does), and engineers wanted to know its "true"
heating effect.

** Nonsense.

Any "moving iron" amp meter inherently reads "true RMS" values and they are
as old as the hills.

True RMS meters are mostly used to measure irregular signals like noise and
distorted current waveforms that exist with AC to DC supply conversion.

There is no way to compute these values ( from the peak or average rectified
value) as there is with sine or other regular waveforms.


..... Phil
 
M

Maynard A. Philbrook Jr.

Jan 1, 1970
0
You'll not get rid of me that easily. I've already had cancer and
Obamacare promises to keep me alive forever.

I'll be more than happy to put a Obama chia pet on your grave stone
for you.

I see Amazon has a deal for 28 bucks..

Jamie
 
M

Maynard A. Philbrook Jr.

Jan 1, 1970
0
Why do you keep quoting notes from Llewelen? He wrote a modeling program
for wire antennas. We are talking about FETs.

I think AVG = RMS only if waveform is pure sinewave. Otherwise you must
use calorimeter or thermocouple to find true RMS.

AVG and RMS is not the same with sine waves..

Avg = 2/pi * peak Voltage.

And RMS is simply sqr( VP^2 / 2).
you'll notice the root his to look for the square not the
average of total voltage for example.

One can shorten that to say RMS = Vp * .707

Just think of a half round circle an draw and find the
area where you can evenly fit a square box in that half circle,
the value will be .707 times the Peak value of that circle.

Averaging ends up to be 2/pi = 0.637 * the peak voltage which
obviously gives you a different number..

And of course, no matter how you slice it, square waves at 50%
duty give you the same all around. AVG and RMS = peak.. cause there
is no slope in time for the avg and the nice square box I stated
fits perfectly in the already square wave for RMS. etc..

Jamie
 
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