the amp is the symmetrical amplifier (designed by Anthony Holton) http://www.aussieamplifiers.com/symmetric.htm
it's possible?
it's possible?
I couldn't find any datasheets for IRF240/9240 (searching the
web suggested they are obsolete) but the general answer
would be no, you can probably not use them. Lateral MOSFETs
start to have a negative temp. coefficient already at rather
small Id, so usually no temp. compensation of the bias is
necessary, and indeed Holton's amp follows this practice.
Although I don't know about the IRF240/9240, most, if not
all, non-lateral MOSFETs have a positive temp. coefficient up
to quite high values of Id, several Ampéres, so I would think
they need temp. compensation of the bias.
Perhaps Nelson, or someone else, can give a good reason why
it might work anyway, but the safe general recommendation
would be not to try it.
web suggested they are obsolete) but the general answer
would be no, you can probably not use them. Lateral MOSFETs
start to have a negative temp. coefficient already at rather
small Id, so usually no temp. compensation of the bias is
necessary, and indeed Holton's amp follows this practice.
Although I don't know about the IRF240/9240, most, if not
all, non-lateral MOSFETs have a positive temp. coefficient up
to quite high values of Id, several Ampéres, so I would think
they need temp. compensation of the bias.
Perhaps Nelson, or someone else, can give a good reason why
it might work anyway, but the safe general recommendation
would be not to try it.
I found a datasheet for IRF240:
http://circuit.codns.com/data/DataSheet/FET/IRF240.PDF
Hehe... the temerature coefficient doesn't become negative before 11 amps...
tino96: Is it the Symmetric amplifier or the Lateral amplifier you are talking about?
The symmetric amplifier uses a Vbe multiplier, and maybe mounting that together with the transistors would be enough to compensate it... but the other one uses just a pot, and that is probably bad. Another thing is the gate-source voltage of the lateral mosfets are much lower. around 0.5V at 100ma for the lateral mosfets and around 4V for the other one...
http://circuit.codns.com/data/DataSheet/FET/IRF240.PDF
Hehe... the temerature coefficient doesn't become negative before 11 amps...
tino96: Is it the Symmetric amplifier or the Lateral amplifier you are talking about?
The symmetric amplifier uses a Vbe multiplier, and maybe mounting that together with the transistors would be enough to compensate it... but the other one uses just a pot, and that is probably bad. Another thing is the gate-source voltage of the lateral mosfets are much lower. around 0.5V at 100ma for the lateral mosfets and around 4V for the other one...
Ooops 
I read the number Christer wrote and didn't check what the OP had written.
IRFP240:
http://www.fairchildsemi.com/ds/IR/IRFP240.pdf
I read the number Christer wrote and didn't check what the OP had written.IRFP240:
http://www.fairchildsemi.com/ds/IR/IRFP240.pdf
If you want to substitute lateral mosfets for vertical mosfets such IRFxxx, you have to :
1) Insert suitable resistors in source, in order to lower and linearize the transconductance at the previous values (0.5 to 1 ohm)
2) Carefully design a suitable temperature coefficient compensation system, because of the high temperature coefficient of the vertical mosfets.
3) Reconsider the phase correction at high frequencies, to keep away HF parasitic oscillations, and maintain decent response for square wave with any kind of load.
But you cannot totally cancel some sort of transient thermal crossover distortion, because of the unavoidable delay between thermal variations (caused by musical transients) and the temperature compensation. This is the reason why lateral mosfets, which needs no compensation, gives superior sound quality in high-end audio.
Apologies for mispelling, etc, too...
Regards, Pierre Lacombe.
1) Insert suitable resistors in source, in order to lower and linearize the transconductance at the previous values (0.5 to 1 ohm)
2) Carefully design a suitable temperature coefficient compensation system, because of the high temperature coefficient of the vertical mosfets.
3) Reconsider the phase correction at high frequencies, to keep away HF parasitic oscillations, and maintain decent response for square wave with any kind of load.
But you cannot totally cancel some sort of transient thermal crossover distortion, because of the unavoidable delay between thermal variations (caused by musical transients) and the temperature compensation. This is the reason why lateral mosfets, which needs no compensation, gives superior sound quality in high-end audio.
Apologies for mispelling, etc, too...
Regards, Pierre Lacombe.
It seems I made a mistake. I checked the schematic of Holtons
symmetric amp and didn't see the Vbe multiplier since it was
drawn so far away from the output stage. I only saw the zeners
and thought they were used to give a constant voltage between
the gates. That changes the matter, and I suppose one could
use ordinary MOSFETs then.
It also seems I misread the MOSFET names. I would guess that
IRFP240 is a plastic case version of an earlier and now obsolete
metal can IRF240. Anyway it esplains why I didin't find a
datasheet.
symmetric amp and didn't see the Vbe multiplier since it was
drawn so far away from the output stage. I only saw the zeners
and thought they were used to give a constant voltage between
the gates. That changes the matter, and I suppose one could
use ordinary MOSFETs then.
It also seems I misread the MOSFET names. I would guess that
IRFP240 is a plastic case version of an earlier and now obsolete
metal can IRF240. Anyway it esplains why I didin't find a
datasheet.
Banned
Joined 2002
I think that the builder of www.aussieamplifiers.com should email me back as i had questions and same with the other person that bought boards. I think that his lack of work and help should be changed. He never replys to emails or any thing. i bought av800 boards and have questions. BUT yet has he replyed to my emails. THIS SUX. i paid good money for these boards and no support at all. : O (
tino96 said:
I would expect that it is possible. Anything is possible. If you do replace the fets, start with the bias current low.
I use IRFP240/9240's a lot. I really like them. The can be run without temp compensation if you bais them low, but it's not recomended. The can and do sometimes thermally runaway.
As Nelson said, the Vgs may be of concern... ...but nothing that can't be delt with.
-Dan
P.S. Everyone... ...I'm back. (One magazine article down, and boards are now etched for the AMP!)
tino96 said:
You may want to check out the SemeLab lateral MOSFETs:
http://www.magnatec-uk.co.uk/mosdata.shtml
The 901DP/906DP are most likely what you're looking for, although especially neat are the 90*X4S series -- 500W per device!
Here is the schematic that you need
Follow this link to the updated schematic that Anthony describes in the construction notes. This is the updated schematic that contains the re-worked bias circuit to handle the IRF FETs.
http://aussieamplifiers.com/images/mosamp8.jpg
Follow this link to the updated schematic that Anthony describes in the construction notes. This is the updated schematic that contains the re-worked bias circuit to handle the IRF FETs.
http://aussieamplifiers.com/images/mosamp8.jpg
The mosamp is the Symmetrical 400 Watt amplifier
http://www.aussieamplifiers.com/downloads/symamp.pdf
(last rev. by Anthony Eric Holton 8 th February 2001)
I'm talking about the Anthony Eric Holton 's 50w to 200w Lateral MOSFET Amplifier; (http://www.aussieamplifiers.com/downloads/chepamp.pdf)
For precision, I have some Faichild's irfP240 and irfP9240 (plastic case) and no IRF240 (metal TO3)
The first amp have too power (and too power devices)
I need an ampli for Transformer with a Core rating of 300 VA.
http://www.aussieamplifiers.com/downloads/symamp.pdf
(last rev. by Anthony Eric Holton 8 th February 2001)
I'm talking about the Anthony Eric Holton 's 50w to 200w Lateral MOSFET Amplifier; (http://www.aussieamplifiers.com/downloads/chepamp.pdf)
For precision, I have some Faichild's irfP240 and irfP9240 (plastic case) and no IRF240 (metal TO3)
The first amp have too power (and too power devices)
I need an ampli for Transformer with a Core rating of 300 VA.
hi. many tnx to all;
I'm talking about the Hitachi 50w to 200w Lateral MOSFET Amplifier
(http://www.aussieamplifiers.com/downloads/chepamp.pdf)
the mosamp8 is the Symmetrical 400 Watt Amplifier
(http://www.aussieamplifiers.com/downloads/symamp.pdf) and is too power for my Transformer 300VA;
I have some Fairchild's IRFP240 an IRFP9240 plastic case and no irf240 (TO3).
If is not possible to adapt my devices, someone have a good schematic?
....and PCB
I'm talking about the Hitachi 50w to 200w Lateral MOSFET Amplifier
(http://www.aussieamplifiers.com/downloads/chepamp.pdf)
the mosamp8 is the Symmetrical 400 Watt Amplifier
(http://www.aussieamplifiers.com/downloads/symamp.pdf) and is too power for my Transformer 300VA;
I have some Fairchild's IRFP240 an IRFP9240 plastic case and no irf240 (TO3).
If is not possible to adapt my devices, someone have a good schematic?
....and PCB
Banned
Joined 2002
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