Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Class D Switching Power Amplifiers and Power D/A conversion

P channel class d anyone ?
P channel class d anyone ?
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
Thread Tools Search this Thread
Old 6th September 2010, 06:29 PM   #1
Tekko is offline Tekko
Join Date: Jan 2005
Default P channel class d anyone ?

Today in lack of anything to do i decided to revisit a cheapo class d topology that i've seen in manuals for flat screen tv's and such.

This is the circuit:
Click the image to open in full size.

I call it the "Cheapo s**t class d"
Since i dident intend this as a project, i dident put down much time in layouting, so heres a video of what i ended up with:
YouTube - Simple quick and dirty class d amplifier

Its running at around 600kHz, but started out at over 1MHz so i had to slow it down a bit. The fets are IRF9540 and IRF540.

Sound ? Pretty darn good for such a lashup, the low frequency response is wicked, it goes right down to DC!!!

In which thread was the similar circuits posted ? I can't remember.
  Reply With Quote
Old 7th September 2010, 05:01 AM   #2
savu is offline savu  Romania
diyAudio Member
savu's Avatar
Join Date: Feb 2007
Location: Cluj - Napoca
Send a message via MSN to savu
fredos did something similar a couple of years ago
1'st rule of chess:
The only way to get smarter is by playing a smarter opponent.
  Reply With Quote
Old 7th September 2010, 05:24 AM   #3
stocktrader200 is offline stocktrader200  Canada
diyAudio Member
Join Date: Jan 2008
Location: Calgary
I have been thinking of a P channel high side to replace the
high side driver and N channel fet.
I'll bet the specs are better then average due to your high switching rate.
  Reply With Quote
Old 7th September 2010, 06:22 AM   #4
Tekko is offline Tekko
Join Date: Jan 2005
Not quite, with a LM311 you cant get below around 0.1% THD due to its internal construction.

Above 400kHz is really just a waste of switching instants, since 300-400kHz is fully enough to produce a 0.01% THD or better full range class d amplifier.

Also, the P channel fet class d is not a good design, it was simply used because high side gate drivers dident exist back then and noone had yet figured out how to drive a high side N channel fet.

Why this kinda circuit is still in use in commercial products is that it dramatically reduces production costs.
  Reply With Quote
Old 7th September 2010, 07:41 AM   #5
phase_accurate is offline phase_accurate
diyAudio Member
Join Date: May 2002
Location: Switzerland
Just wanted to remind you that the IR2110 already existed more than 20 years ago ! The current versions have better specs though.

Because I didn't like how it behaved back then I did an amp with complementary output stage as well. It had a DC path parallel to the capaciator coupling. And it wasn't self osciallating. The schematic can be found somewhere on this forum.


  Reply With Quote
Old 7th September 2010, 10:38 AM   #6
Eva is offline Eva  Spain
diyAudio Member
Eva's Avatar
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
This circuit demands clean, damped and very low impedance supply rails. Otherwise signal-dependent and load-dependent parasitic turn-on of the wrong MOSFET can arise.

In fact, the power supply is in series with gate drive.
I use to feel like the small child in The Emperor's New Clothes tale
  Reply With Quote
Old 7th September 2010, 11:55 AM   #7
Tekko is offline Tekko
Join Date: Jan 2005
Yeh its not a good design. I'm not gonna waste time on making any boards for this one, just play with when nothing else to do.
  Reply With Quote
Old 7th September 2010, 03:29 PM   #8
Sch3mat1c is offline Sch3mat1c  United States
diyAudio Member
Sch3mat1c's Avatar
Join Date: Jan 2003
Location: Milwaukee, WI
Send a message via ICQ to Sch3mat1c Send a message via AIM to Sch3mat1c
It works better from the same rail, low voltage only. That way you don't have to worry about Vgs(max) or DC restoration hacks (as shown).

For most MOSFETs, you need shorting-mode commutation, because Vgs(th) is small and shoot-through occurs when both transistors are switching.

My block-model class D amp seems to be working fairly well, by the way. "Complementary" H bridge output.

Seven Transistor Labs, LLC
Projects and Resources / Electronic Design and Consultation
  Reply With Quote
Old 7th September 2010, 06:30 PM   #9
Tekko is offline Tekko
Join Date: Jan 2005
I have been messing around with it some more and eventually damaged something which caused the amp to temporarily stick to one of the rails above a certain volume, so i decided to short the speaker terminals and see what would happen, volume on max and heavy clipping and rail sticking, whilest still on a heatsink it just kept on going, got hot but nothing else.

I've never before had an amplifier survive full volume into a dead short!
  Reply With Quote
Old 7th September 2010, 07:43 PM   #10
m-tech is offline m-tech  Serbia
diyAudio Member
Join Date: Feb 2006
Location: Belgrade
A year ago I made similar amp ( on single sided PCB ). Sound is quite nice ( for me ), but I never done any measurements.
Attached Images
File Type: jpg 1.jpg (101.3 KB, 410 views)
File Type: jpg 2.jpg (54.9 KB, 373 views)

Last edited by m-tech; 7th September 2010 at 07:51 PM.
  Reply With Quote


P channel class d anyone ?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
8 Channel Class D Based on TAS5706A aramosfet Class D 3 12th April 2009 08:37 AM
want to make a class T 6 channel scott262 Class D 0 22nd November 2008 08:05 PM
Class D amp, one channel ... funky. guitarcarl Class D 1 20th November 2008 09:57 PM
6 Channel Class D? AudioX Class D 3 4th February 2008 04:53 AM
Multi-channel Class A from ApexJr X-Formers? Dustin Haug Pass Labs 5 1st March 2002 05:00 PM

New To Site? Need Help?

All times are GMT. The time now is 09:39 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio