Which N Or P Power MOSFETs ?...

[Jeff Urban]

Many know I set out to build a really good amp. Well after all that I found it can\'t work. The drawing was on the bench and I saw the problem immediately, at a glance. Damn.

But I did find it. Now it needs power MOSFETs for outputs. This looks pretty much non-negotiable.

I forget which is which but they are all the same. Al either ?N channel or P channel. The difference it the power supply. Which is easier to design, but what if the better choice need negative, ? Then I draw it upside down, so what ?

So which is better or more linear or whatever ?

We are in the 140V/18A range.

 

[Clive Arthur]

On 19/11/2020 12:25, Jeff Urban wrote:

Many know I set out to build a really good amp. Well after all that I found it can\'t work. The drawing was on the bench and I saw the problem immediately, at a glance. Damn.

But I did find it. Now it needs power MOSFETs for outputs. This looks pretty much non-negotiable.

I forget which is which but they are all the same. Al either ?N channel or P channel. The difference it the power supply. Which is easier to design, but what if the better choice need negative, ? Then I draw it upside down, so what ?

So which is better or more linear or whatever ?

We are in the 140V/18A range.

I thought we\'d done with Trump, but it seems he\'s decided to post here :-(

--
Cheers
Clive

 

[Bill Sloman]

On Thursday, November 19, 2020 at 11:25:48 PM UTC+11, Jeff Urban wrote:

Many know I set out to build a really good amp. Well after all that I found it can\'t work. The drawing was on the bench and I saw the problem immediately, at a glance. Damn.

But I did find it. Now it needs power MOSFETs for outputs. This looks pretty much non-negotiable.

I forget which is which but they are all the same. Al either ?N channel or P channel. The difference it the power supply. Which is easier to design, but what if the better choice need negative, ? Then I draw it upside down, so what ?

So which is better or more linear or whatever ?

We are in the 140V/18A range.

One way of making a decent class-AB audio output stage used complementary pairs of power FET - a P-channel device with it\'s source tied to the positive rail, and and N-channel device with it\'s source tied to the negative rail..

You use bipolar transistors to monitor the current being fed into the speakers and generated the gate drives for the power MOSFETs. The tricky bit is keeping both MOS-FETs just on when the output is half-way between the rails.. People like Douglas Self have written reams on the subject.

Buy one of his books, or one of his amplifiers. The amplifier will work better than anything you can build for yourself, and by the time you\'ve blown up a few big power MOSFET\'s it will also turn out to be the cheaper option.

If you are very lucky, Phil Allison will chip in here. He won\'t be polite but his well-informed.

--
Bill Sloman, Sydney

 

[George Herold]

On Thursday, November 19, 2020 at 7:25:48 AM UTC-5, Jeff Urban wrote:

Many know I set out to build a really good amp. Well after all that I found it can\'t work. The drawing was on the bench and I saw the problem immediately, at a glance. Damn.

But I did find it. Now it needs power MOSFETs for outputs. This looks pretty much non-negotiable.

I forget which is which but they are all the same. Al either ?N channel or P channel. The difference it the power supply. Which is easier to design, but what if the better choice need negative, ? Then I draw it upside down, so what ?

So which is better or more linear or whatever ?

We are in the 140V/18A range.

Is this a linear amp? If so that\'s a lot of heat.
Do you have \"Art of Electronics\". (The 2nd ed. is probably fairly cheap now.)

George H.

 

[server]

On Thu, 19 Nov 2020 05:31:20 -0800 (PST), George Herold
<ggherold@gmail.com> wrote:

On Thursday, November 19, 2020 at 7:25:48 AM UTC-5, Jeff Urban wrote:
Many know I set out to build a really good amp. Well after all that I found it can\'t work. The drawing was on the bench and I saw the problem immediately, at a glance. Damn.

But I did find it. Now it needs power MOSFETs for outputs. This looks pretty much non-negotiable.

I forget which is which but they are all the same. Al either ?N channel or P channel. The difference it the power supply. Which is easier to design, but what if the better choice need negative, ? Then I draw it upside down, so what ?

So which is better or more linear or whatever ?

We are in the 140V/18A range.
Is this a linear amp? If so that\'s a lot of heat.
Do you have \"Art of Electronics\". (The 2nd ed. is probably fairly cheap now.)

George H.

The problem is not well specified. \"Good amp\" is not very clear.

Class-D amps are simple and efficient. I\'m designing one right now.

Most mosfets are designed for switching and don\'t take kindly to
linear operation, way out there on their SOAR curve. They tend to blow
up at some fraction of their rated power dissipation; bipolars do that
too.

We learned about that.

https://www.dropbox.com/s/4nxm7m2q3j3buvc/ExFets.jpg?raw=1



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[George Herold]

On Thursday, November 19, 2020 at 10:37:06 AM UTC-5, jla...@highlandsniptechnology.com wrote:

On Thu, 19 Nov 2020 05:31:20 -0800 (PST), George Herold
gghe...@gmail.com> wrote:

On Thursday, November 19, 2020 at 7:25:48 AM UTC-5, Jeff Urban wrote:
Many know I set out to build a really good amp. Well after all that I found it can\'t work. The drawing was on the bench and I saw the problem immediately, at a glance. Damn.

But I did find it. Now it needs power MOSFETs for outputs. This looks pretty much non-negotiable.

I forget which is which but they are all the same. Al either ?N channel or P channel. The difference it the power supply. Which is easier to design, but what if the better choice need negative, ? Then I draw it upside down, so what ?

So which is better or more linear or whatever ?

We are in the 140V/18A range.
Is this a linear amp? If so that\'s a lot of heat.
Do you have \"Art of Electronics\". (The 2nd ed. is probably fairly cheap now.)

George H.
The problem is not well specified. \"Good amp\" is not very clear.

Class-D amps are simple and efficient. I\'m designing one right now.

Most mosfets are designed for switching and don\'t take kindly to
linear operation, way out there on their SOAR curve. They tend to blow
up at some fraction of their rated power dissipation; bipolars do that
too.

We learned about that.

https://www.dropbox.com/s/4nxm7m2q3j3buvc/ExFets.jpg?raw=1



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

Here\'s a crazy idea... ( idea stolen from a linear power supply with stepped taps
on the transformer.) How about a linear amp (inner loop) with some switched
power supply rails... ? It would probably be ugly.
George H.

 

[Ed Lee]

On Thursday, November 19, 2020 at 4:59:52 AM UTC-8, Clive Arthur wrote:

On 19/11/2020 12:25, Jeff Urban wrote:

Many know I set out to build a really good amp. Well after all that I found it can\'t work. The drawing was on the bench and I saw the problem immediately, at a glance. Damn.

But I did find it. Now it needs power MOSFETs for outputs. This looks pretty much non-negotiable.

I forget which is which but they are all the same. Al either ?N channel or P channel. The difference it the power supply. Which is easier to design, but what if the better choice need negative, ? Then I draw it upside down, so what ?

So which is better or more linear or whatever ?

We are in the 140V/18A range.

I thought we\'d done with Trump, but it seems he\'s decided to post here :-(

Why? Because our president-elected is bipolar?

 

[Piglet]

On 19/11/2020 15:52, George Herold wrote:

On Thursday, November 19, 2020 at 10:37:06 AM UTC-5, jla...@highlandsniptechnology.com wrote:
On Thu, 19 Nov 2020 05:31:20 -0800 (PST), George Herold
gghe...@gmail.com> wrote:

On Thursday, November 19, 2020 at 7:25:48 AM UTC-5, Jeff Urban wrote:
Many know I set out to build a really good amp. Well after all that I found it can\'t work. The drawing was on the bench and I saw the problem immediately, at a glance. Damn.

But I did find it. Now it needs power MOSFETs for outputs. This looks pretty much non-negotiable.

I forget which is which but they are all the same. Al either ?N channel or P channel. The difference it the power supply. Which is easier to design, but what if the better choice need negative, ? Then I draw it upside down, so what ?

So which is better or more linear or whatever ?

We are in the 140V/18A range.
Is this a linear amp? If so that\'s a lot of heat.
Do you have \"Art of Electronics\". (The 2nd ed. is probably fairly cheap now.)

George H.
The problem is not well specified. \"Good amp\" is not very clear.

Class-D amps are simple and efficient. I\'m designing one right now.

Most mosfets are designed for switching and don\'t take kindly to
linear operation, way out there on their SOAR curve. They tend to blow
up at some fraction of their rated power dissipation; bipolars do that
too.

We learned about that.

https://www.dropbox.com/s/4nxm7m2q3j3buvc/ExFets.jpg?raw=1



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard
Here\'s a crazy idea... ( idea stolen from a linear power supply with stepped taps
on the transformer.) How about a linear amp (inner loop) with some switched
power supply rails... ? It would probably be ugly.
George H.

Yep, it\'s been done already. Goes by weird names like class \"H\" or \"G\"
or whatever marketing thinks sounds cool.

piglet

 

[Piglet]

On 19/11/2020 12:25, Jeff Urban wrote:

Many know I set out to build a really good amp. Well after all that I found it can\'t work. The drawing was on the bench and I saw the problem immediately, at a glance. Damn.

But I did find it. Now it needs power MOSFETs for outputs. This looks pretty much non-negotiable.

I forget which is which but they are all the same. Al either ?N channel or P channel. The difference it the power supply. Which is easier to design, but what if the better choice need negative, ? Then I draw it upside down, so what ?

So which is better or more linear or whatever ?

We are in the 140V/18A range.

Instead of going straight for 140V/18A try your ideas first as a
headphone amp then you can use little TO-92 fets in white proto-board
and each burnout only wastes cents?

piglet

 

[server]

On Thu, 19 Nov 2020 16:54:26 +0000, Piglet <erichpwagner@hotmail.com>
wrote:

On 19/11/2020 12:25, Jeff Urban wrote:

Many know I set out to build a really good amp. Well after all that I found it can\'t work. The drawing was on the bench and I saw the problem immediately, at a glance. Damn.

But I did find it. Now it needs power MOSFETs for outputs. This looks pretty much non-negotiable.

I forget which is which but they are all the same. Al either ?N channel or P channel. The difference it the power supply. Which is easier to design, but what if the better choice need negative, ? Then I draw it upside down, so what ?

So which is better or more linear or whatever ?

We are in the 140V/18A range.


Instead of going straight for 140V/18A try your ideas first as a
headphone amp then you can use little TO-92 fets in white proto-board
and each burnout only wastes cents?

piglet

140 * 18 = 2520. Think big heat sinks.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[server]

On Thu, 19 Nov 2020 12:59:43 +0000, Clive Arthur
<clive@nowaytoday.co.uk> wrote:

On 19/11/2020 12:25, Jeff Urban wrote:

Many know I set out to build a really good amp. Well after all that I found it can\'t work. The drawing was on the bench and I saw the problem immediately, at a glance. Damn.

But I did find it. Now it needs power MOSFETs for outputs. This looks pretty much non-negotiable.

I forget which is which but they are all the same. Al either ?N channel or P channel. The difference it the power supply. Which is easier to design, but what if the better choice need negative, ? Then I draw it upside down, so what ?

So which is better or more linear or whatever ?

We are in the 140V/18A range.


I thought we\'d done with Trump, but it seems he\'s decided to post here :-(

I thought nobody would volunteer to turn a technical thread into
politics.

Thanks for stepping up.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[George Herold]

On Thursday, November 19, 2020 at 11:51:58 AM UTC-5, piglet wrote:

On 19/11/2020 15:52, George Herold wrote:
On Thursday, November 19, 2020 at 10:37:06 AM UTC-5, jla...@highlandsniptechnology.com wrote:
On Thu, 19 Nov 2020 05:31:20 -0800 (PST), George Herold
gghe...@gmail.com> wrote:

On Thursday, November 19, 2020 at 7:25:48 AM UTC-5, Jeff Urban wrote:
Many know I set out to build a really good amp. Well after all that I found it can\'t work. The drawing was on the bench and I saw the problem immediately, at a glance. Damn.

But I did find it. Now it needs power MOSFETs for outputs. This looks pretty much non-negotiable.

I forget which is which but they are all the same. Al either ?N channel or P channel. The difference it the power supply. Which is easier to design, but what if the better choice need negative, ? Then I draw it upside down, so what ?

So which is better or more linear or whatever ?

We are in the 140V/18A range.
Is this a linear amp? If so that\'s a lot of heat.
Do you have \"Art of Electronics\". (The 2nd ed. is probably fairly cheap now.)

George H.
The problem is not well specified. \"Good amp\" is not very clear.

Class-D amps are simple and efficient. I\'m designing one right now.

Most mosfets are designed for switching and don\'t take kindly to
linear operation, way out there on their SOAR curve. They tend to blow
up at some fraction of their rated power dissipation; bipolars do that
too.

We learned about that.

https://www.dropbox.com/s/4nxm7m2q3j3buvc/ExFets.jpg?raw=1



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard
Here\'s a crazy idea... ( idea stolen from a linear power supply with stepped taps
on the transformer.) How about a linear amp (inner loop) with some switched
power supply rails... ? It would probably be ugly.
George H.

Yep, it\'s been done already. Goes by weird names like class \"H\" or \"G\"
or whatever marketing thinks sounds cool.

piglet

Thanks piglet, you can tell I\'m an audio expert. :^)
Not much when searching for class G/H but this seems good.
https://sound-au.com/articles/class-g.htm

GH

 

[bitrex]

On 11/19/2020 10:36 AM, jlarkin@highlandsniptechnology.com wrote:

On Thu, 19 Nov 2020 05:31:20 -0800 (PST), George Herold
ggherold@gmail.com> wrote:

On Thursday, November 19, 2020 at 7:25:48 AM UTC-5, Jeff Urban wrote:
Many know I set out to build a really good amp. Well after all that I found it can\'t work. The drawing was on the bench and I saw the problem immediately, at a glance. Damn.

But I did find it. Now it needs power MOSFETs for outputs. This looks pretty much non-negotiable.

I forget which is which but they are all the same. Al either ?N channel or P channel. The difference it the power supply. Which is easier to design, but what if the better choice need negative, ? Then I draw it upside down, so what ?

So which is better or more linear or whatever ?

We are in the 140V/18A range.
Is this a linear amp? If so that\'s a lot of heat.
Do you have \"Art of Electronics\". (The 2nd ed. is probably fairly cheap now.)

George H.

The problem is not well specified. \"Good amp\" is not very clear.

Class-D amps are simple and efficient. I\'m designing one right now.

Most mosfets are designed for switching and don\'t take kindly to
linear operation, way out there on their SOAR curve. They tend to blow
up at some fraction of their rated power dissipation; bipolars do that
too.

We learned about that.

https://www.dropbox.com/s/4nxm7m2q3j3buvc/ExFets.jpg?raw=1

Vertical MOSFETs when used as linear amps have basically all the same
problems BJTs can have, thermal runaway and second breakdown.

Lateral MOSFETs are more well-behaved but there are few of them on the
market and they tend to be filthy expensive.

 

[bitrex]

On 11/19/2020 1:34 PM, bitrex wrote:

On 11/19/2020 10:36 AM, jlarkin@highlandsniptechnology.com wrote:
On Thu, 19 Nov 2020 05:31:20 -0800 (PST), George Herold
ggherold@gmail.com> wrote:

On Thursday, November 19, 2020 at 7:25:48 AM UTC-5, Jeff Urban wrote:
Many know I set out to build a really good amp. Well after all that
I found it can\'t work. The drawing was on the bench and I saw the
problem immediately, at a glance. Damn.

But I did find it. Now it needs power MOSFETs for outputs. This
looks pretty much non-negotiable.

I forget which is which but they are all the same. Al either ?N
channel or P channel. The difference it the power supply. Which is
easier to design, but what if the better choice need negative, ?
Then I draw it upside down, so what ?

So which is better or more linear or whatever ?

We are in the 140V/18A range.
Is this a linear amp?  If so that\'s a lot of heat.
Do you have \"Art of Electronics\".  (The 2nd ed. is probably fairly
cheap now.)

George H.

The problem is not well specified. \"Good amp\" is not very clear.

Class-D amps are simple and efficient. I\'m designing one right now.

Most mosfets are designed for switching and don\'t take kindly to
linear operation, way out there on their SOAR curve. They tend to blow
up at some fraction of their rated power dissipation; bipolars do that
too.

We learned about that.

https://www.dropbox.com/s/4nxm7m2q3j3buvc/ExFets.jpg?raw=1




Vertical MOSFETs when used as linear amps have basically all the same
problems BJTs can have, thermal runaway and second breakdown.

Lateral MOSFETs are more well-behaved but there are few of them on the
market and they tend to be filthy expensive.

The drive requirements for vertical MOSFETs as linear amps at high
powers isn\'t much improved with respect to BJTs, either.

 

[bitrex]

On 11/19/2020 11:54 AM, Piglet wrote:

On 19/11/2020 12:25, Jeff Urban wrote:

Many know I set out to build a really good amp. Well after all that I
found it can\'t work. The drawing was on the bench and I saw the
problem immediately, at a glance. Damn.

But I did find it. Now it needs power MOSFETs for outputs. This looks
pretty much non-negotiable.

I forget which is which but they are all the same. Al either ?N
channel or P channel. The difference it the power supply. Which  is
easier to design, but what if the better choice need negative, ? Then
I draw it upside down, so what ?

So which is better or more linear or whatever ?

We are in the 140V/18A range.


Instead of going straight for 140V/18A try your ideas first as a
headphone amp then you can use little TO-92 fets in white proto-board
and each burnout only wastes cents?

piglet

Or just a 50 watt amp. That requires what, about +/- 35 volt rails to
deliver 20 VRMS into an 8 ohm load.

Differential input stage feeding a bootstrap VAS followed by a 2N3055
Darlington and a 2N3055 Sziklai to make a PNP is a classic. 8
transistors if you use a current source for the input pair.

 

[Phil Allison]

bitrex is completely wrong as usual :

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

Vertical MOSFETs when used as linear amps have basically all the same
problems BJTs can have, thermal runaway and second breakdown.

** Yeah right - problems that were solved 40 years ago.

Lateral MOSFETs are more well-behaved but there are few of them on the
market and they tend to be filthy expensive.

** Neither claim is true.

Both TO3 and flat pak laterals are available at tolerable prices.

Their advantages easily outweigh the extra cost.

...... Phil

 

[Phil Allison]

bitrex is demeted wrote:

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

Or just a 50 watt amp. That requires what, about +/- 35 volt rails to
deliver 20 VRMS into an 8 ohm load.

Differential input stage feeding a bootstrap VAS followed by a 2N3055
Darlington and a 2N3055 Sziklai to make a PNP is a classic. 8
transistors if you use a current source for the input pair.

** Straight out of the Beatles era.

\" Love, love me do.... \"


...... Phil

 

[bitrex]

On 11/19/2020 2:33 PM, Phil Allison wrote:

bitrex is completely wrong as usual :

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

Vertical MOSFETs when used as linear amps have basically all the same
problems BJTs can have, thermal runaway and second breakdown.

** Yeah right - problems that were solved 40 years ago.

Phil\'s behind the times as usual, modern devices like HEXFETs are not
immune (PDF):

<https://toshiba.semicon-storage.com/info/docget.jsp?did=63593>

Lateral MOSFETs are more well-behaved but there are few of them on the
market and they tend to be filthy expensive.

** Neither claim is true.

Both TO3 and flat pak laterals are available at tolerable prices.

Their advantages easily outweigh the extra cost.

..... Phil

Well which do you like?

 

[bitrex]

On 11/19/2020 2:36 PM, Phil Allison wrote:

bitrex is demeted wrote:

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

Or just a 50 watt amp. That requires what, about +/- 35 volt rails to
deliver 20 VRMS into an 8 ohm load.

Differential input stage feeding a bootstrap VAS followed by a 2N3055
Darlington and a 2N3055 Sziklai to make a PNP is a classic. 8
transistors if you use a current source for the input pair.

** Straight out of the Beatles era.

\" Love, love me do.... \"


..... Phil

The power stage in my Onkyo TX 2500 Mk II is very much like that, except
it adds a voltage source bias to give about 35 watts class AB from +/-
40 volt rails. From about 1978 I think. They didn\'t bother with a
current source in the pair tail.

 

[Phil Allison]

bitrex puked more verbal diarrhoea:

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

bitrex is completely wrong as usual :

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

Vertical MOSFETs when used as linear amps have basically all the same
problems BJTs can have, thermal runaway and second breakdown.

** Yeah right - problems that were solved 40 years ago.

Phil\'s behind the times as usual, modern devices like HEXFETs are not
immune (PDF):
https://toshiba.semicon-storage.com/info/docget.jsp?did=63593

** Don\'t ya just love when some know nothing fuckhead like \"bitrex\"\'
chucks a URL at you and says -
\" the proof of my wrong idea is here, go search for it. \"

That is never an *argument* at all and very often, as here, the URL actually contradicts the wrong idea.

Fuck off \" bit brain\" !!!

There are far too may TROLLS like you fucking up the NG.


...... Phil