2SK/irfp lateral vertical mosfet amplifier HELP ??

[medogrizli]

So I am searching for +/70 V Mosfet amplifier schematics

Are 2sk campatibile with irfp240 Can i in certain schematics replace this two mosfet types?

If nost why ?


What are pros and cons of each mosfet type ?

Is there any difference in soud qualitiy


thanks

 

[jackinnj]

the lateral mosfet's are a bit more difficult to find and somewhat more expensive -- but they have the advantage of no thermal runaway.

the bias for lateral mosfets is much, much lower -- reduce the values of the resistors in the VBE multiplier --

 

[medogrizli]

the lateral mosfet's are a bit more difficult to find and somewhat more expensive -- but they have the advantage of no thermal runaway.

the bias for lateral mosfets is much, much lower -- reduce the values of the resistors in the VBE multiplier --

Isnt 2skxxxx lateral ?


Do you have some links where is described the difference between vertical and lateral ?

 

[richie00boy]

2sk/sj are lateral. They don't suffer thermal runaway and are quite linear, they are made for audio. The pinout is GSD.

IRF are vertical. They are made for switching but often used in amps designed properly for them, successfully. The pinout is GDS.

Lateral can be used in an amp for vertical design, but the bias thermal tracking must be attended to and the bias voltage must be lowered. You cannot use vertical in an amp designed for lateral as it will quickly heat up and die.

 

[medogrizli]

2sk/sj are lateral. They don't suffer thermal runaway and are quite linear, they are made for audio. The pinout is GSD.

IRF are vertical. They are made for switching but often used in amps designed properly for them, successfully. The pinout is GDS.

Lateral can be used in an amp for vertical design, but the bias thermal tracking must be attended to and the bias voltage must be lowered. You cannot use vertical in an amp designed for lateral as it will quickly heat up and die.

I can not translate "bias" in my local language : can you describe whats that

Thermal runaway means that they start better conduction drain source when temperature rising : But thats not bad : it can preserve amplifier from breakdown if no properly cooled

So whats the difference in SOUND qualitiy between IRFP and 2SK mosfet amplifier

so can lateral amplifier be modified for using vertical mosfets?

Are there any -/+ good working schematcs for IRFP and 2SK mosfets
here on the forum

thanks

 

[jackinnj]

I can not translate "bias" in my local language : can you describe whats that

Thermal runaway means that they start better conduction drain source when temperature rising : But thats not bad : it can preserve amplifier from breakdown if no properly cooled

So whats the difference in SOUND qualitiy between IRFP and 2SK mosfet amplifier

so can lateral amplifier be modified for using vertical mosfets?

Are there any -/+ good working schematcs for IRFP and 2SK mosfets
here on the forum

thanks

BIAS -- it's just a little voltage to get the device to "go" -- in the case of a MOSFET it gets the device to that point at which it will respond linearly to voltage.

You can adapt an amplifier which used lateral mosfet's to vertical but it will require different bias voltage, and as pointed out previously, the pinouts are different. Among the most popular DIY amps ever built are those by Nelson Pass using the International Rectifier IRFp240 and IRFP9240.

There are a couple of good designs on the Elliot Sound Products website. Other FET designs can be found on PASSDIY and on Erno Borbely's site.

 

[richie00boy]

I can not translate "bias" in my local language : can you describe whats that

It is the 'standing voltage' applied to bring the device just into useful conduction.

Thermal runaway means that they start better conduction drain source when temperature rising : But thats not bad : it can preserve amplifier from breakdown if no properly cooled

Sorry but that is completely wrong. More heat forces more current which makes more heat which forces more current... bang

So whats the difference in SOUND qualitiy between IRFP and 2SK mosfet amplifier

Sound quality is subjective. In my opinion it's as much to do with the amplifier topology as the output devices and other parts.

so can lateral amplifier be modified for using vertical mosfets?

Yes but usually it's not worth the hassle.

Are there any -/+ good working schematcs for IRFP and 2SK mosfets
here on the forum

thanks

Yes there are good, and bad. I'm afraid you will have to search yourself.

 

[Nelson Pass]

You cannot use vertical in an amp designed for lateral as it will quickly heat up and die.

Of course that is not literally correct.

 

[medogrizli]

BIAS -- it's just a little voltage to get the device to "go" -- in the case of a MOSFET it gets the device to that point at which it will respond linearly to voltage.

You can adapt an amplifier which used lateral mosfet's to vertical but it will require different bias voltage, and as pointed out previously, the pinouts are different. Among the most popular DIY amps ever built are those by Nelson Pass using the International Rectifier IRFp240 and IRFP9240.

There are a couple of good designs on the Elliot Sound Products website. Other FET designs can be found on PASSDIY and on Erno Borbely's site.

Do you have schematics of Nelson Pass ? or link?

 

[Leolabs]

Hi,please specified the circuit configuration you are interested,ie single-ended or diffirential amp base input or fully push-pull................

 

[bigpanda]

I have one good for both, call me

tony_chan_cf@email.com

 

[AndrewT]

Hi Nelson,

Of course that is not literally correct

his use of the word

die

although not literally correct implies the correct meaning and considering the construction process seemed quite appropriate.

 

[ilimzn]

Hi,please specified the circuit configuration you are interested,ie single-ended or diffirential amp base input or fully push-pull................

At +-70V rails, yes I am sure he wants single ended

 

[ilimzn]

I can not translate "bias" in my local language : can you describe whats that

Prednapon, ili struja mirovanja.

Thermal runaway means that they start better conduction drain source when temperature rising : But thats not bad : it can preserve amplifier from breakdown if no properly cooled

No, wrong - with higher drain current you get more heat. As you get more heat you get more current, this makes even more heat etc, until eventually you have a case of the magic smoke escaping. The problem is not as big with VMOS, but you may run into a situation where an amplifier that 'worked perfectly but got just a bit hot' suddenly self destructed 'without a reason'.

So whats the difference in SOUND qualitiy between IRFP and 2SK mosfet amplifier

The biggest difference in sound quality comes from the designer of the amp being able to properly use his/hers intended choice of MOSFETs... not to mention all the other parts in the amplifier.

so can lateral amplifier be modified for using vertical mosfets?

Yes, and in most cases the modification looks trivial, but may prove to be more problematic in practise. Also, in some cases the modification may be too extensive to make it worth while - if you want to use your chosen parts in the best way.

Are there any -/+ good working schematcs for IRFP and 2SK mosfets here on the forum

Many, use search. Look at posts from Quasi.
Although his are not complementary amps, given your power supply of +-70V, which should give you about 300W into 8 ohms, such an amp will be easyer to make and cheaper.

BTW regarding lateral / vertical MOSFETs:

Most 2SJ/2SK are vertical MOSFETs. Out of the hundred or so types, only two types made for audio are still available new:

Toshiba 2SJ200/201 + 2SK1529/1530
These are PI-MOS types, which have a trench structure shannel and are NOT lateral. Apart from having a lower treshold voltage (napon praga), they behave like a vertical type. Their gm is also lower but they are better complementaries then the usual IRF/IRFP types.

Hitachi/Renesas 2SJ160/161/162 + 2SK1056/1057/1058
These are lateral types, practically they are equivalent to old style TO3 metal 2SJ56/2SK176, just in a plastic case. These have NEGATIVE drain current coefficient - when their bias current is set to about 100mA per pair, the coefficient is practically zero and at this idle current they are self-stabilizing thermally. You pay for this with lower current handling, lower but more linear gm, and, since they are fairly unique, with a high price.

All the IRFxxxx are vertical type, they need a bias servo similar to what is used with normal bipolar transistors. Their temperature coefficient lowers to zero at about 70-100% max current, which is usually way beyond the point of destruction in a typical amp.

 

[richie00boy]

Thanks Andrew

 

[medogrizli]

Hi,please specified the circuit configuration you are interested,ie single-ended or diffirential amp base input or fully push-pull................

AB class : single ended input +/-70V using vertical mosfet

But you can aloso post differential input amplifier : isnt it easy to make into single ended?

(irfp )


push-pull ? D-class ?

 

[medogrizli]

No, wrong - with higher drain current you get more heat. As you get more heat you get more current, this makes even more heat etc, until eventually you have a case of the magic smoke escaping. The problem is not as big with VMOS, but you may run into a situation where an amplifier that 'worked perfectly but got just a bit hot' suddenly self destructed 'without a reason'.

So lets compare this to bipolars !

How is that with power amplifiers usnig bipolars they do not suffer this temperature runaway : ?

Many, use search. Look at posts from Quasi.
Although his are not complementary amps, given your power supply of +-70V, which should give you about 300W into 8 ohms, such an amp will be easyer to make and cheaper.

imposibble: max 200W 8 ohm that is not bipolar ?!
300W How? i

Hitachi/Renesas 2SJ160/161/162 + 2SK1056/1057/1058
These are lateral types, practically they are equivalent to old style TO3 metal 2SJ56/2SK176, just in a plastic case. These have NEGATIVE drain current coefficient - when their bias current is set to about 100mA per pair, the coefficient is practically zero and at this idle current they are self-stabilizing thermally. You pay for this with lower current handling, lower but more linear gm, and, since they are fairly unique, with a high price.

So how is achieved this termal stabilising with lateral mosfet design?


So when using irfp is it always necesarry temperature control ? mountig some other "elemont" near oputput mosfets be heated as output mosfets are heated and so controls current thorugh them

 

[medogrizli]

So what about this schematics?

Hitachi/Renesas 2SJ160/161/162 + 2SK1056/1057/1058
These are lateral types, practically they are equivalent to old style TO3 metal 2SJ56/2SK176, just in a plastic case. These have NEGATIVE drain current coefficient - when their bias current is set to about 100mA per pair, the coefficient is practically zero and at this idle current they are self-stabilizing thermally. You pay for this with lower current handling, lower but more linear gm, and, since they are fairly unique, with a high price.

He is using irfp mosfets

 

[medogrizli]

neglect post above

So what about this schematics?
http://users.swing.be/edwinpaij/ampli_mosfet_360_w.htm

I see only resistor for setting bias current ?

If using really good "Cooler" heatsink fot output stages is this temperature cotroled bias really neccesary

And another question : Can you describe sound compared bipolar to mosfet amplifier: PLEAS TRY to describe it with words allthough it seems difficult to describe

 

[ilimzn]

neglect post above

So what about this schematics?
http://users.swing.be/edwinpaij/ampli_mosfet_360_w.htm

I see only resistor for setting bias current?

Why not ask the author?
All I can give youis an opinion, and this is that I would never build an amp that way, for several reasons some of which I will explain below.

If using really good "Cooler" heatsink fot output stages is this temperature cotroled bias really neccesary

Nothing is 'necessary' - assuming you are willing to accept the consequences.
For instance, it is possible to reduce the thermal co-efficient to a level where it does not result in output stage destruction? Of course - using low bias current, sufficiently large source resistors and a sufficiently large heatsink will result in the temperature rise being below a treshold of failure. But, you may get a suboptimal heatsink (too large), potential unreliability if it ever becomes obstructed, and, an unstable bias current. The later will have repercussions to the distortion performance. And for what? Saving one transistor and 2-3 resistors???

And another question : Can you describe sound compared bipolar to mosfet amplifier: PLEAS TRY to describe it with words allthough it seems difficult to describe

Hehe describe to me the sound of a non-mosfet amp and I will describe to you the sound of a MOSFET amp. There are as many 'sounds' as there are amps and I am not sure I can give a specific character to MOSFET amps. I could say that most of the MOSFET amps I have heared that I would say were 'good' tended to sound slightly more 'withdrawn', or, perhaps, better said, less forward in the midrange than bipolar transistor amps - but I can't say that either way is better.