output network

icko · 12th September 2008, 01:54 AM

Iam trying to build a subwoofer amp using TDA8920BJ IC and I am trying to figure out some stuff from the schematic in the datasheet.

And I can't understand what resistors R14,R9 and cap C24,C32 do. Anybody know?

After looking around in application note for phillips class d amplifier they are sometimes omitted and sometimes only on one of the outputs. Both for BTL applications.
http://www.nxp.com/acrobat_download/.../AN10436_1.pdf

djQUAN · 12th September 2008, 03:48 AM

they are there so that the output stage doesn't blow up when the amp is powered without any load or drives a reactive load.

sawreyrw · 12th September 2008, 05:00 AM

These components damp the output LC filters. Without these there would be severe ringing or overshoot at the natural frequency of the filter.

icko · 12th September 2008, 07:03 AM

thanks!

icko · 12th September 2008, 01:00 PM

Can somebody explain what the symbols at each input is?

I assume that the half-circle denotes the input but the circle with ground through the circle and on top of it. Is it an american standard symbol?

darkfenriz · 12th September 2008, 01:22 PM

RC is to diminish the Q of the filter for not very resistive loads. Speakers are highly inductive above audio.

The symbols are typical schematic symbol for a jack socket.

Adam

icko · 12th September 2008, 02:07 PM

no matter. i figured it out

icko · 13th September 2008, 02:38 PM

Thanks for all replies so far.

My highly speculative calculations show that the highest current will be around 7 A through the output network.

Anybody knows where to buy an inductor with ~25-16 uH that is capable of those currents? Best i've come up with are http://www.coilws.com/ but their shipping prices are horrifific.

Where do you buy your filter inductors?

guitar_joe · 13th September 2008, 03:14 PM

heya,
where do you buy the TDA8920?

cheers

icko · 13th September 2008, 05:07 PM

haven't bought it yet but i plan to buy it via nxp website.

12th September 2008, 01:54 AM	#1
icko diyAudio Member Join Date: Sep 2008	output network Iam trying to build a subwoofer amp using TDA8920BJ IC and I am trying to figure out some stuff from the schematic in the datasheet. And I can't understand what resistors R14,R9 and cap C24,C32 do. Anybody know? After looking around in application note for phillips class d amplifier they are sometimes omitted and sometimes only on one of the outputs. Both for BTL applications. http://www.nxp.com/acrobat_download/.../AN10436_1.pdf

13th September 2008, 02:38 PM	#8
icko diyAudio Member Join Date: Sep 2008	Power Inductor Thanks for all replies so far. My highly speculative calculations show that the highest current will be around 7 A through the output network. Anybody knows where to buy an inductor with ~25-16 uH that is capable of those currents? Best i've come up with are http://www.coilws.com/ but their shipping prices are horrifific. Where do you buy your filter inductors?

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Input / Output impedance, Resistor network Vs. Dynamics	-_nando-_	Everything Else	3	24th March 2007 11:19 PM
advise on 2/3 way network	kdlsrinu	Multi-Way	8	24th August 2005 07:53 AM
BHC T-Network caps	Fiberbyte	Parts	0	26th January 2005 10:48 AM
Aleph 5--CRC network	billy	Pass Labs	2	24th June 2004 02:57 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	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

12th September 2008, 03:48 AM	#2
djQUAN diyAudio Member Join Date: May 2004 Location: manila	they are there so that the output stage doesn't blow up when the amp is powered without any load or drives a reactive load.

12th September 2008, 05:00 AM	#3
sawreyrw diyAudio Member Join Date: Apr 2006 Location: Minnesota	These components damp the output LC filters. Without these there would be severe ringing or overshoot at the natural frequency of the filter.

12th September 2008, 07:03 AM	#4
icko diyAudio Member Join Date: Sep 2008	thanks!

12th September 2008, 01:00 PM	#5
icko diyAudio Member Join Date: Sep 2008	Can somebody explain what the symbols at each input is? I assume that the half-circle denotes the input but the circle with ground through the circle and on top of it. Is it an american standard symbol?

12th September 2008, 01:22 PM	#6
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	RC is to diminish the Q of the filter for not very resistive loads. Speakers are highly inductive above audio. The symbols are typical schematic symbol for a jack socket. Adam

12th September 2008, 02:07 PM	#7
icko diyAudio Member Join Date: Sep 2008	no matter. i figured it out

13th September 2008, 03:14 PM	#9
guitar_joe diyAudio Member Join Date: May 2007	heya, where do you buy the TDA8920? cheers

13th September 2008, 05:07 PM	#10
icko diyAudio Member Join Date: Sep 2008	haven't bought it yet but i plan to buy it via nxp website.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)