Irf9640 - diyAudio
Go Back   Home > Forums > Design & Build > Parts

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

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 28th November 2004, 08:10 AM   #1
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Default Irf9640

Q is it normal for IRF640 to have much better current and Rds(on) than the complimentary IRF9640?
From the retailers data table they are not good compliments!
I have seen a reference to amp design using more Pchannel fets than Nchannel.
Q is this an attempt to balance the current capacity?
regards Andrew T.
  Reply With Quote
Old 29th November 2004, 12:48 PM   #2
quasi is offline quasi  Australia
diyAudio Member
 
quasi's Avatar
 
Join Date: Sep 2004
Location: Adelaide, Australia
Default Hey AndrewT;

The only real match is the power rating at 125W. So this could be the reason they are nominated as complimentary. I.e to allow designers to build amps (and similar ccts) knowing the power rating is the same for both rails.

The input capacitance is similar for both devices. This is important for a symmetrical load on the driver stages.

The Rds-on for P channel devices from IRF is always higher for some reason, but I think this would only be an issue if the FETS were saturated (clipping). The amp you see with more P channel devices would probably be an attempt to match the total Rds-on with the N device side. This will cause however a mismatch in the input capacitance (can be fixed with an external capacitor).


Cheers
  Reply With Quote
Old 29th November 2004, 12:54 PM   #3
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
It's harder to make p-channel MOSFETs so these devices are never as good as their n-ch counterparts. Hence why SMPS almost always use just n-ch.
  Reply With Quote
Old 29th November 2004, 05:05 PM   #4
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
sounds like it's normal for N & P channel to be a poor match.
Q Is this why Nchannel power amps are popular? (I have been following a couple of long threads on this recently).
Q Does the poor matching affect the quality of the sound? or is this more down to the quality of the design feeding the FETs?
thanks so far Andrew T.
  Reply With Quote
Old 29th November 2004, 05:14 PM   #5
djQUAN is offline djQUAN  Philippines
diyAudio Member
 
Join Date: May 2004
Location: manila
Send a message via MSN to djQUAN Send a message via Yahoo to djQUAN
Quote:
Q Is this why Nchannel power amps are popular? (I have been following a couple of long threads on this recently).
based on my experience, N channel mosfets are cheaper, easier to obtain, more power handling ability in comparison to P channel devices.
  Reply With Quote
Old 29th November 2004, 10:38 PM   #6
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
Quote:
Originally posted by AndrewT
Hi,
sounds like it's normal for N & P channel to be a poor match.
Q Is this why Nchannel power amps are popular? (I have been following a couple of long threads on this recently).
Q Does the poor matching affect the quality of the sound? or is this more down to the quality of the design feeding the FETs?
thanks so far Andrew T.
The preceeding circuitry (actually all the clever bit that does the error correction) will always have an effect on the sound, as will the output stage. It's logical to suppose that both these things could have an equal effect upon the sound.

Generally vertical MOSFETs (IRF and the like) are not all that complementary between n-ch and p-ch. Proper audio lateral MOSFETs (Exicon etc.) are much better in that respect. Bipolars are better still. That's not to say though that you can't make a great amp with IRFs, because you can.

As well as the equality in a complementary pair for output stages, you need to consider a whole load of other factors such as transconductance and overall linearity.
  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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Irf9640 pnut028 Parts 1 14th January 2006 12:16 PM


New To Site? Need Help?

All times are GMT. The time now is 09:16 PM.


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