Tyimo said:
You have the formula.
You still haven't told me what heatsink you have.
Mad_K. or maybe somebody else,
suggested something like 0.25 C/W sink.
( if you do not know number of yours, 0.3 C/W for example can have a weight of 2.5-3.0 kg )
What good if I give you formulas
if you have to ask questions
instead of doing some easy calculations ..
------------------------------------------------
If using only one + one IRFP254N and a big (0.3) heatsink we get the following coefficients:
Rsa = 0.3
Rcs = 0.4 ( Insulator AlOxide + thermal grease )
Rjc = 0.68 (IRFP254N)
---------------------
Air temp 30 degrees.
110 watt in heatsink = 33 degrees
55 watt in Insulator = 22 degrees
55 watt in each FET = 37.4 degrees
---------------------
Sum it up, and you have the junction temp.
Not the exact temp, but a good hint what it will be like.
Then it is up to you to decide if that temp is too high or not.
And to decide if you want to use only 2 or go for 4 IRFP254N.
I say with a very very big heasink!!!!!!!
it will work with 2.
But if you want amplifier to work good ( lower distortion )
you should probably use 4 x IRFP254N.
Another option is to use 4 of some other IRFP.
When using 4 you have many different you can use:
IRFP240, 140 150 etc ....
Maybe even TO220: IRF640 ... ????
But might not be wise for 110 Watt idle .....
will be 27.5 Watt per device.
regards
lineup --- heading for shopping some food, in order to eat & survive
Hi!
I calculated my Heatsinks with Rod Elliot's Heatsinks calculator.
The result is good: under 0.25C/W!
I shall continue to calculating with 1 IRFP254N in the CCS and 2 other device on the top.
What do you think? Am I a sick perverse???
O.K. I tell you my reason why I want to use this: I only have 2 pair of matched IRFP240 and I would like to use them for the SEWA SE or SEWAPLUS!
Tyimo
I calculated my Heatsinks with Rod Elliot's Heatsinks calculator.
The result is good: under 0.25C/W!
I shall continue to calculating with 1 IRFP254N in the CCS and 2 other device on the top.
What do you think? Am I a sick perverse???
O.K. I tell you my reason why I want to use this: I only have 2 pair of matched IRFP240 and I would like to use them for the SEWA SE or SEWAPLUS!
Tyimo
Re: Boz
No.
Not that I can see.
If you need a preamplfier with a voltage gain of x10 (+20dB)
then BoZ would work alright
in almost any sound system as line level preamp.
You can use output to feed one Volume potentiometer 5kohm-100kohm.
The original uses one 10uF output capacitor
into one 5kohm volume control at output.
If your sound source, CD, DVD or whatever has got Volume control, remote or not,
you can connect BoZ output directly to a normal power amplifier input.
If you decide build one BoZ, we are many that can support you.
Because many members have already built this project
and knows anything you want to know.
And if we do not know
the master himself,
the designer Nelson Pass might jump in and tell
lineup .... in AC-län vid Ume-älven
zei said:
No.
Not that I can see.
If you need a preamplfier with a voltage gain of x10 (+20dB)
then BoZ would work alright
in almost any sound system as line level preamp.
You can use output to feed one Volume potentiometer 5kohm-100kohm.
The original uses one 10uF output capacitor
into one 5kohm volume control at output.
If your sound source, CD, DVD or whatever has got Volume control, remote or not,
you can connect BoZ output directly to a normal power amplifier input.
If you decide build one BoZ, we are many that can support you.
Because many members have already built this project
and knows anything you want to know.
And if we do not know
the master himself,
the designer Nelson Pass might jump in and tell
lineup .... in AC-län vid Ume-älven
HI
I've been interested in the "power follower" idea for quite a while
I've done a headphone amplifier using that topology and modified it very often. (it use the irf610)
It's reasonable to think that the improvement I made in my headphone amp will translate in the sewa.
2 best upgrade I've done aren't present in the sewa...
1- get rid of the output capacitor. The use of a DC servo with op-amp do easely that job. (of course, you need dual power supply)
Using orcad, I draw the basic schematic of a DC servo.
the op-amp isn't in the signal loop and DC ofset should be less than 3 mV
Sorry, the picture isn't very clear... (I copy/paste using Paint)
2- the current source benefit from some more accurate topology.
the best one imho is done with the tl431.
http://www.fairchildsemi.com/ds/TL/TL431A.pdf
Look on the datasheet on page 6, figure 14 for detail.
I've been interested in the "power follower" idea for quite a while
I've done a headphone amplifier using that topology and modified it very often. (it use the irf610)
It's reasonable to think that the improvement I made in my headphone amp will translate in the sewa.
2 best upgrade I've done aren't present in the sewa...
1- get rid of the output capacitor. The use of a DC servo with op-amp do easely that job. (of course, you need dual power supply)
Using orcad, I draw the basic schematic of a DC servo.
the op-amp isn't in the signal loop and DC ofset should be less than 3 mV
Sorry, the picture isn't very clear... (I copy/paste using Paint)
2- the current source benefit from some more accurate topology.
the best one imho is done with the tl431.
http://www.fairchildsemi.com/ds/TL/TL431A.pdf
Look on the datasheet on page 6, figure 14 for detail.
Attachments
Build a 25 Watt power amplifier.
okay
I didnt get anything more than that index.htm, with no links.
Mads K. Madsen, Denmark
... this is most probably another Mads K.
But nevertheless he has got DIY Amplifier website.
Welcome to WebAudio's Homepage
I remember I have visited this Mads pages some years ago.
The most interesting, is maybe:
Build a 25 Watt power amplifier.
Try something simple for a change!
It is a very good article about a nice amplifier project.
Schematics, explanations and pictures.
lineup
okay
I didnt get anything more than that index.htm, with no links.
Mads K. Madsen, Denmark
... this is most probably another Mads K.
But nevertheless he has got DIY Amplifier website.
Welcome to WebAudio's Homepage
I remember I have visited this Mads pages some years ago.
The most interesting, is maybe:
Build a 25 Watt power amplifier.
Try something simple for a change!
It is a very good article about a nice amplifier project.
Schematics, explanations and pictures.
An externally hosted image should be here but it was not working when we last tested it.
lineup
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