Bridge and Parrallel Output Resistors.
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 15th February 2004, 07:52 PM #1 Matttcattt   diyAudio Member     Join Date: Feb 2003 Location: Bristol Bridge and Parrallel Output Resistors. When bridging and paralleling four or more chips (OPA541 in this case), resistors are required to connect the outputs of the chips (see image). I am building an amp using bridging and paralleling, and I hope it to produce 150W+ into 8ohms. On the circuit diagram I am following, 10W resistors are specified. All of the output power from the chips goes through these resistors, so in theory, I need ~40W resistors, or I will have to limit my output power to 40W. Has anyone else thought along these lines, or am I being stupid, and I have nothing to worry about? __________________ If it aint broke, don't fix it. If it is broke, fix it. If you can't fix it, take it apart and see how it "worked".
Matttcattt
diyAudio Member

Join Date: Feb 2003
Location: Bristol
oops, forgot the image.
Attached Images
 resistors.gif (17.5 KB, 155 views)
__________________
If it aint broke, don't fix it. If it is broke, fix it.
If you can't fix it, take it apart and see how it "worked".

 15th February 2004, 08:51 PM #3 peranders   Electrons are yellow and more is better! diyAudio Member     Join Date: Apr 2002 Location: Göteborg, Sweden 1 How much current will flow through the resistors at full output load? 2 Which value did you have in mind for these resistors? EDIT: 100 mohms. 3 How much power will each resistor develop? Something to think about. __________________ /Per-Anders (my first name) or P-A as my friends call me Group buy: DCT03 DC trap for big toroidal transformers. Sign up for interest HERE. 65 pcb's in order. 59 paid.
GregGC
diyAudio Member

Join Date: Oct 2003
Location: Toronto
Re: Bridge and Parrallel Output Resistors.

Quote:
 Originally posted by Matttcattt When bridging and paralleling four or more chips (OPA541 in this case), resistors are required to connect the outputs of the chips (see image). I am building an amp using bridging and paralleling, and I hope it to produce 150W+ into 8ohms. On the circuit diagram I am following, 10W resistors are specified. All of the output power from the chips goes through these resistors, so in theory, I need ~40W resistors, or I will have to limit my output power to 40W. Has anyone else thought along these lines, or am I being stupid, and I have nothing to worry about?

You'll get a rough idea as a percent of the load power. If your load is 8 ohms and you use 2x0.1ohm/leag res. than your power dissipation is 8/0.1=80 times less than the load, so for 100W/80=1.3W over a 0.1ohm resistor. I think 0.1ohm/2W res will do fine for 100W/8ohm load.

Matttcattt
diyAudio Member

Join Date: Feb 2003
Location: Bristol
Re: Re: Bridge and Parrallel Output Resistors.

Quote:
 Originally posted by GregGC You'll get a rough idea as a percent of the load power. If your load is 8 ohms and you use 2x0.1ohm/leag res. than your power dissipation is 8/0.1=80 times less than the load, so for 100W/80=1.3W over a 0.1ohm resistor. I think 0.1ohm/2W res will do fine for 100W/8ohm load.
ok

im just being stupid
__________________
If it aint broke, don't fix it. If it is broke, fix it.
If you can't fix it, take it apart and see how it "worked".

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