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What characterizes a powerFET for audio use?

P

Phil Allison

Jan 1, 1970
0
"Maynard A. Philbrook Jr."
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 ...

** Too complicated.

Q. When you ( full wave) rectify a square wave what do you get?

A. DC.

With DC, the average, peak and RMS value are the same.

Is any proof really needed ?




...... Phil
 
P

Phil Allison

Jan 1, 1970
0
"Maynard A. Philbrook Jr."
And where was I disputing that?


** Yawnnnnnnnnn - wot a stupid straw man fallacy.

Read what I dam well wrote - fuckwit.



.... Phil
 
M

Maynard A. Philbrook Jr.

Jan 1, 1970
0
"Maynard A. Philbrook Jr."

** Too complicated.

Q. When you ( full wave) rectify a square wave what do you get?

A. DC.

With DC, the average, peak and RMS value are the same.

Is any proof really needed ?




..... Phil

And where was I disputing that?

Jamie
 
P

Phil Allison

Jan 1, 1970
0
"Shaun"
I used to work at an Industrial and Instrumentation repair and Calibration
shop that was licensed by Beckman to repair and calibrate there DMMs. In
the good ones, the RMS converted used a thermal method to determine RMS
Voltage and Current. That was 18 years ago and I don't remember any
details except that they used thermal measurement on a heated element. I
have compared the reading on the Beckman - Then Wavetek - now I don't know
if anyone is still making them, to a Fluke RMS DMM at 60 Hz and DC and the
readings matched.

** No fooling...........
I have always heard that if you really want to know the real value, you
have to buy an RMS meter.

** That sort of nonsense *would* be said by someone who either owned an RMS
meter or was selling them.

Thermal RMS meters are virtually obsolete these days and have been replaced
by cheap analogue RMS to DC computation ICs in many hand held DMMs OR by
digital sampling computation in most DSOs.

The hand held kind have a limited measurement bandwidth compared to the
latter.

Depends what your needs are.

As Clint Eastwood might have said -

" Man's gotta know the limitations of his test equipment ".




..... Phil
 
P

Phil Allison

Jan 1, 1970
0
dave the autistic fool said:
In television you calibrate the output power metering by operating into a
full power liquid cooled dummy load and measuring the temperature of the
coolant.

** That would be for the actual transmitter on VHF or UHF - right ?

Same idea as using a glass of water and a thermometer test the power RF
power of a microwave oven.

Got SFA to do with the topic.



..... Phil
 
P

Phil Allison

Jan 1, 1970
0
"dave the pig ignorant autistic IDIOT "

The question was why is audio power spec is half that of DC on/off
capability.

** No it was not.

It is because the device stays on all the time and because the audio
waveform causes more heating.


** A maker's max dissipation spec for a semiconductor is not related to the
application.

It is only related to the device itself.

Normally, the figure given is for *ideal* operating conditions - like when
mounted on an infinite heatsink held at 20C.



..... Phil
 
L

Leif Neland

Jan 1, 1970
0
Phil Allison skrev:
Same idea as using a glass of water and a thermometer test the power RF power
of a microwave oven.

Just don't leave the thermometer in the microwave oven with the power
on.

Measure the temperature of the cold water, then measure the time for it
to boil.

Preferably in a microwave-safe plastic container.

I measured the power of my previous oven to 230W...

Leif
 
M

mike

Jan 1, 1970
0
Phil Allison skrev:

Just don't leave the thermometer in the microwave oven with the power on.

Measure the temperature of the cold water, then measure the time for it
to boil.

Preferably in a microwave-safe plastic container.

I measured the power of my previous oven to 230W...

Leif
When I did similar tests, I found the order of magnitude was right,
but the result depended on the shape and volume of the mass of water
and position in the oven.

It's easy to imagine that the microwaves bounce around and most of the
energy ends up
in the water. Wonder how accurate that model?
Wonder what the "official" water configuration is when they determine
the spec?
 
S

Shaun

Jan 1, 1970
0
"mike" wrote in message
Phil Allison skrev:

Just don't leave the thermometer in the microwave oven with the power on.

Measure the temperature of the cold water, then measure the time for it
to boil.

Preferably in a microwave-safe plastic container.

I measured the power of my previous oven to 230W...

Leif
When I did similar tests, I found the order of magnitude was right,
but the result depended on the shape and volume of the mass of water
and position in the oven.

It's easy to imagine that the microwaves bounce around and most of the
energy ends up
in the water. Wonder how accurate that model?
Wonder what the "official" water configuration is when they determine
the spec?

I've seen that method used before. I had an article about measuring
microwave oven power. You of course measure the increase in temperature
after running then microwave oven for a predetermine time at full power,
with a measured amount of water (distilled) in the direct center of the
oven. You could google it.

Shaun
 
P

Phil Allison

Jan 1, 1970
0
"Leif Neland"
Phil Allison

Just don't leave the thermometer in the microwave oven with the power on.

** Should be OK with a glass tube and red liquid type.

Measure the temperature of the cold water, then measure the time for it to
boil.

** Bad idea.

Takes far too long, when boiling first begins is not clear and lots of heat
is lost to the air and evaporation.

I measured the power of my previous oven to 230W...

** Using half a litre in a plastic jug for two minutes, I got the answer to
within 10% with a 700W rated oven.

Having a K-type bead thermocouple and digital temp meter made the job easier
too.



..... Phil
 
S

Shaun

Jan 1, 1970
0
"Phil Allison" wrote in message

"Leif Neland"
Phil Allison

Just don't leave the thermometer in the microwave oven with the power on.
** Should be OK with a glass tube and red liquid type.

Measure the temperature of the cold water, then measure the time for it to
boil.

** Bad idea.
Takes far too long, when boiling first begins is not clear and lots of heat
is lost to the air and evaporation.

I measured the power of my previous oven to 230W...
** Using half a litre in a plastic jug for two minutes, I got the answer to
within 10% with a 700W rated oven.
Having a K-type bead thermocouple and digital temp meter made the job
easier
too.

You don't run it till boiling! once you get close to boiling point a lot of
extra energy is required to raise it further and make it boil. What you do
is run a glass of cold distilled water measured (temp and volume) in a
container, you could use several stacked Styrofoam cups for insulation and
cover the top with Styrofoam so that the heat generated does not escape and
run the oven till the temperature increase 20 to 50 degrees or so, then
measure the temp, the information will have an equation to convert degrees
rise to microwave power. Google the method - I haven't looked it up lately.

Shaun



..... Phil
 
S

Shaun

Jan 1, 1970
0
"Shaun" wrote in message


"Phil Allison" wrote in message

"Leif Neland"
Phil Allison

Just don't leave the thermometer in the microwave oven with the power on.
** Should be OK with a glass tube and red liquid type.

Measure the temperature of the cold water, then measure the time for it to
boil.

** Bad idea.
Takes far too long, when boiling first begins is not clear and lots of heat
is lost to the air and evaporation.

I measured the power of my previous oven to 230W...
** Using half a litre in a plastic jug for two minutes, I got the answer to
within 10% with a 700W rated oven.
Having a K-type bead thermocouple and digital temp meter made the job
easier
too.

You don't run it till boiling! once you get close to boiling point a lot of
extra energy is required to raise it further and make it boil. What you do
is run a glass of cold distilled water measured (temp and volume) in a
container, you could use several stacked Styrofoam cups for insulation and
cover the top with Styrofoam so that the heat generated does not escape and
run the oven till the temperature increase 20 to 50 degrees or so, then
measure the temp, the information will have an equation to convert degrees
rise to microwave power. Google the method - I haven't looked it up lately.

Shaun



Here is the Method from RepairFAQ from Sam:



7.1) Testing the oven - the water heating test


The precise number of degrees a known quantity of water increases in
temperature for a known time and power level is a very accurate test of
the actual useful microwave power. A couple of minutes with a cup of
water and a thermometer will conclusively determine if your microwave
oven is weak or you are just less patient (or the manufacturer of your
frozen dinners has increased their weight - sure, fat chance of that!)

You can skip the heavy math below and jump right to the final result
if you like. However, for those who are interested:

* 1 Calorie (C) will raise the temperature of 1 gram (g) of liquid water
exactly 1 degree Centigrade (DegC) or 9/5 degree Fahrenheit (DegF).

* 1 Calorie is equal to 4.184 Joules (J) or 1 J = .239 C.

* 1 Watt (W) of power is 1 J/s or 1 KW is 1000 J/s.

* 1 cup is 8 ounces (oz) which is 8 x 28.35 g/oz = 226.8 g.

* 1 minute equals 60 s (but you know this!).

Therefore, in one minute, a 1 KW microwave oven will raise the temperature
of 1 cup of water by:

T(rise) = (60 s * 1000 J/s * .239C/J * (g * DegC)/C)/(226.8 g) = 63
DegC.

Or, if your prefer Fahrenheit: 114 DegF.

To account for estimated losses due to conduction, convection, and imperfect
power transfer, I suggest using temperature rises of 60 DegC and 109 DegF.

Therefore, a very simple test is to place a measured cup of water in the
microwave from the tap and measure its temperature before and after heating
for exactly 1 minute on HIGH. Scale the expected temperature rise by the
ratio of the microwave (not AC line) power of your oven compared to a 1 KW
unit.

Or, from a Litton microwave handbook:

Heat one Liter (L) of water on HIGH for 1 minute.

Oven power = temperature rise in DegC multiplied by 70.

Use a plastic container rather than a glass one to minimize the needed
energy loss to raise its temperature by conduction from the hot water.
There will be some losses due to convection but this should not be that
significant for these short tests.

(Note: if the water is boiling when it comes out - at 100 DegC or 212 DegF,
then the test is invalid - use colder water or a shorter time.)

The intermediate power levels can be tested as well. The heating effect of
a microwave oven is nearly linear. Thus, a cup of water should take nearly
roughly twice as long to heat a specific number of degrees on 50% power or
3.3 times as long on 30% power as on full power. However, for low power
tests, increasing the time to 2 minutes with 2 cups of water will result
in more accurate measurements due to the long period pulse width power
control use by microwave ovens which may have a cycle of up to 30 seconds.

Any significant discrepancy between your measurements and the specified
microwave power levels - say more than 10 % on HIGH - may indicate a
problem.
(Due to conduction and convection losses as well as the time required to
heat the filament of the magnetron for each on-cycle, the accuracies of
the intermediate power level measurements may be slightly lower).

Shaun
 
J

Jeff Urban

Jan 1, 1970
0
I wanted to reply to this when you first posted it but I couldn't for
whatever reason. fucking thing. As you can see I am not posting from
google, which I no longer capitalize !!!! LOL

Anyway, what characterizes ANY part for the transmission of audio is
linearity. Even though the gate of a MOSFET is driven wildly different
than the base of a BPT, linearity of gain fro the very small signal to
the very large signal is the prime. We used to look at the hfe and HFE
gain curves of bipolars in the old days, not it is different.

Any kinds of spurious shit like oscillations would be no good in
switcxhers as well. the thing is, switchers somethimes have a gain curve
that is like, made to be on or off.

An audio transistor must operate in the analog range, that means the
gain curve should be as flat as possible through the operating current
range.

The same is true of a MOSFET.
 
N

N_Cook

Jan 1, 1970
0
I wanted to reply to this when you first posted it but I couldn't for
whatever reason. fucking thing. As you can see I am not posting from
google, which I no longer capitalize !!!! LOL

Anyway, what characterizes ANY part for the transmission of audio is
linearity. Even though the gate of a MOSFET is driven wildly different
than the base of a BPT, linearity of gain fro the very small signal to
the very large signal is the prime. We used to look at the hfe and HFE
gain curves of bipolars in the old days, not it is different.

Any kinds of spurious shit like oscillations would be no good in
switcxhers as well. the thing is, switchers somethimes have a gain curve
that is like, made to be on or off.

An audio transistor must operate in the analog range, that means the
gain curve should be as flat as possible through the operating current
range.

The same is true of a MOSFET.

Ah at last , thanks, a pertinent reply to my original question. I was
wondering if it was a larger area of silicon so the heat can migrate out
of the die quicker. So from what you say a non-audio switcher mosfet
could be used for analogue but the power rating would have to be derated
and no other qualification for such use, anymore than usual precautions
you would use for a switcher situation. I suppose the amount of derating
would then depend on the type of use bass amp v GP audio amp, dance
music v classical music etc
 
P

Phil Allison

Jan 1, 1970
0
"Nutcase Kook is yet another 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

Ah at last , thanks, a pertinent reply to my original question.


** There is no possible answer to a question as wrong headed and stupid as
that.

So you will never get one.

FOAD you vile pommy cunthead.




..... Phil
 
N

N_Cook

Jan 1, 1970
0
I wanted to reply to this when you first posted it but I couldn't for
whatever reason. fucking thing. As you can see I am not posting from
google, which I no longer capitalize !!!! LOL

Anyway, what characterizes ANY part for the transmission of audio is
linearity. Even though the gate of a MOSFET is driven wildly different
than the base of a BPT, linearity of gain fro the very small signal to
the very large signal is the prime. We used to look at the hfe and HFE
gain curves of bipolars in the old days, not it is different.

Any kinds of spurious shit like oscillations would be no good in
switcxhers as well. the thing is, switchers somethimes have a gain curve
that is like, made to be on or off.

An audio transistor must operate in the analog range, that means the
gain curve should be as flat as possible through the operating current
range.

The same is true of a MOSFET.

or on rereading . If an audio application can tolerate a certain amount
of cross-over distortion and general harmonic distortion then there is
no difference in powerfet useage type , up to some power level where
these distortions become too apparent.
 
Shaun said:
When I did similar tests, I found the order of magnitude was right,
but the result depended on the shape and volume of the mass of water
and position in the oven. [...]

Wonder what the "official" water configuration is when they determine
the spec?

I don't know about a US Federal Trade Commission (or other agency, or
equivalent in other countries) test procedure; there probably is one but
I don't know it.

I know that older GE microwave ovens, in the little service information
sheet that was folded up inside the oven, gave directions on the test, a
GE part number for a beaker you were supposed to use, and I think a
third-party part number for the thermometer you were supposed to use to
measure the water temperature before and after. I think the water level
was marked on the beaker, and the service sheet said to put it right in
the middle of the oven. You didn't boil it, just heated it for a fixed
amount of time.

If I remember right, the criteria was something like "if the oven
produced between X and Y degrees temperature rise in the water, it's
within spec" - it didn't give you an answer in watts, just an acceptable
temperature range for that particular model oven.

Matt Roberds
 
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