My MOSFET amplifier designed for music. - Page 9 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 10th June 2008, 11:18 AM   #81
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
Quote:
Originally posted by Lumba Ogir
Obviously
Lumba,

lateral MOSFETs have an equivalent fT in the 100MHz range, as mentioned.
Vertical MOSFETs manage about three times as much, around 300MHz equivalent.
Which fairly corresponds with the ratios of the switching and rise times of both MOSFET types.
There's not an fT with MOSFETs, as there's no hFe, equivalent fT for a MOSFET is derived by Gm/(2*Pi*Cgs)

Once you found your brain in your private tete-a-tete at the HA-larious Colangelo thread, do try a search for a sense of humor.
__________________
The buck stops Here
  Reply With Quote
Old 10th June 2008, 11:38 AM   #82
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Hi guys,
This speed thing ! My maths is useless, so if what I am saying is a load of tripe please do say so
The gate is seen as a capacitance. To swing say 10 volts in 180nS ( This is max on time from the data sheet under specific conditions and I just picked this as a value to work with) equates to 55 volts per microsecond. If the capacitance is 1 nF that means a current source is needed that will supply 55 mA current to give that rate of change of voltage on the gate. That takes some doing at that speed.
Does that sound reasonable or have I lost the plot already
There has to be more to it than this though because if this were the only requirement then why does the off time not equal the on time-- 60 nS is all that is needed to turn it off. Charging and discharging a cap is "symmetrical" time wise. As the FET does not suffer from hole storage effects like the Bjt what causes this effect ?
  Reply With Quote
Old 10th June 2008, 11:59 AM   #83
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Hello Nigel,
I do understand what you are saying about ground planes, and it will give a lower overall impedance which is very beneficial in many applications, but with audio the devil is in the detail as far as where the best points to return various components to are.
It's a bit like with the feedback take off point mentioned earlier, there was plenty of copper there, but if you connected a 'scope to that print and could move the probe around it the signal would be constantly changing. We tend to think of copper as zero ohms but it's anything but. If the board is double sided there is also the possibilty of the ground plane effecting the circuit due to capacitive coupling between the two halves.
No easy answer and there is no right and wrong way, both have advantages and disadvantages.
Regards Karl
  Reply With Quote
Old 10th June 2008, 06:23 PM   #84
Banned
 
Join Date: Apr 2005
Location: Stockholm
Jacco,
please read and learn

Ode to Lateral MOSFETs
  Reply With Quote
Old 11th June 2008, 11:09 AM   #85
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
Per-Anders is an EE and has been building lateral MOSFET output stages for +2 decades.
Yet he speaks little, as so often, and asks you instead of talking a great deal.
What does that tell you : a sign of ignorance, or a modest display of intelligence ?

You claimed that the extreme high speed of Lateral MOSFETs is part of the reason for them being THE superior audio output devices, yet Vertical MOSFETs are so much faster.
What really sets Lateral MOSFETs apart from Verticals is their very awkward transconductance behaviour at high frequencies, stuff that has also been posted here several years ago.(eg jcx, i think)

Something you did not mention in your very antique smelling Pain serenade, antique as in "heard it all 20 years ago".
You seem to enjoy to talk a lot but rarely care to listen, still an abundance of young buck hormones i guess, old folks like P-A and me unfortunately lost them somewhere along the trail.
__________________
The buck stops Here
  Reply With Quote
Old 12th June 2008, 04:55 AM   #86
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
Quote:
Originally posted by Lumba Ogir
peranders,

It would be more beneficial to start exploring the properties of the lateral and vertical structure. After that you may never think about using verticals in audio circuits again.

It's a rather unusual claim to say that laterals are faster than verticals and since I work as an design engineer where I have heard the opposite I would very much like to hear some evidence of your claim.

Even the heavy dude Bob Cordell says this:
"The drain-gate capacitance of verticals is not a big problem if the right kind of drivers are used. Verticals are fundamentally much faster than laterals in terms of equivalant ft."
http://www.diyaudio.com/forums/showt...54#post1536554
__________________
/Per-Anders (my first name) or P-A as my friends call me
Tube Buffered Gainclone in work |Thread || Diamond buffer |Thread for the group buy | Wiki
  Reply With Quote
Old 12th June 2008, 05:02 AM   #87
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
Quote:
Originally posted by jacco vermeulen
Per-Anders is an EE and has been building lateral MOSFET output stages for +2 decades.
Yet he speaks little, as so often, and asks you instead of talking a great deal.
What does that tell you : a sign of ignorance, or a modest display of intelligence ?

You seem to enjoy to talk a lot but rarely care to listen, still an abundance of young buck hormones i guess, old folks like P-A and me unfortunately lost them somewhere along the trail.
Indeed and I'll get a bit suspicious like you Jacco. Here is a man that won't even hint why he thinks the opposite and still it's not "it sounds better", it's facts!

In the world I am in laterals are not very much faster than verticals.
__________________
/Per-Anders (my first name) or P-A as my friends call me
Tube Buffered Gainclone in work |Thread || Diamond buffer |Thread for the group buy | Wiki
  Reply With Quote
Old 12th June 2008, 07:51 AM   #88
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
And now for something completely different

----- HAS NO ONE BUILT IT YET. -----
  Reply With Quote
Old 12th June 2008, 08:18 AM   #89
KLe is offline KLe  Australia
Banned
 
Join Date: Jul 2005
Location: Brisbane
Hi Mooly,

alex mm in underway, I hope

  Reply With Quote
Old 15th June 2008, 12:22 PM   #90
diyAudio Member
 
Join Date: Mar 2008
hi mooly,

finally my parts has arives. should i follow your first posted circuit deisgn?

tell you one joke, Today i just tried to make class a simple circuit just for fun, using 2sk1058, the sound quality i really didin't like it, thou it was single ended class A amp. i want to ask you one question, does class A amp sound really good? honestly tells you i never heard class A amp sound ecpt mine ugly. i know yours is not class A. i will make one class A amp after i finish yours. i am thinking to make aleph-x...still far far away....ha.ha...have to learn more right...


Best regards
michael
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 12:38 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2