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Old 4th August 2012, 08:54 PM   #2161
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Quote:
Originally Posted by stewin View Post
hi whortless

which is the best transistor to use as buffer in totem pole . to drive 4 pairs irfb 4227 or irfp250 or irfp264 or (irf640 6pairs)?? will the 2SB772/2SD882 work or there is a better pair.
Hi,

I never used totem pole drivers after a specially designed IC. Never need to use one except the previous discrete UCD amps. However, They should be high HFE and low Vce sat. ones. They should be for switching purpose. The Vce of the complementary pairs are not so important if they can work within the Vboost or Vdrive voltage range. Hence, the pairs i suggested can do the job. In my previous designs i used philips 5240T as fast turn off. And used Maxim 7.2A SOT23 mosfet driver to drive heavy mosfets like IRFP250.
In my view BD911/912 can be used as an output of a 50-70W class AB amp and using them as totem pole drivers not a logical approach to Class-D design. There are several BJTs around from Sanken, ZETEX or Philips for this purpose. Try to find out best for your purpose. Try to get a set of transistors as samples.

Good luck,

BW
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Old 5th August 2012, 03:36 AM   #2162
paskal9 is offline paskal9  Malaysia
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Originally Posted by exflaco View Post
Dont forget the lower conextion the gnd from v rails to the gnd input (single wire)
have u built it? there's even some difference between the schematic and the pcb. but the most problematic is the cd4049 pinout which is totally different from the datasheet and schematic compared to the pcb. the pcb shouldn't work, but i wonder if anyone did manage to.
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Old 5th August 2012, 06:21 PM   #2163
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i managed to make this thing work but dint get any much success......on low volume it works as clean as a headphone does but when increase volume there is a distortion in the speakers...like someone is tearing papers......help me out with this issue??????
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Old 5th August 2012, 06:52 PM   #2164
stewin is offline stewin  Kenya
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thanks Whortless i,ll try bc327 and bc337 do they meet the requirements?
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Old 5th August 2012, 06:54 PM   #2165
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I use BD244/BD243 with 4 irfb4227.
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Old 5th August 2012, 06:57 PM   #2166
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i managed to make this thing work but dint get any much success......on low volume it works as clean as a headphone does but when increase volume there is a distortion in the speakers...like someone is tearing papers......help me out with this issue??????
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Old 5th August 2012, 07:19 PM   #2167
stewin is offline stewin  Kenya
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Originally Posted by nigelwright7557 View Post
I use BD244/BD243 with 4 irfb4227.
they are same as tip41 and tip42?

Last edited by stewin; 5th August 2012 at 07:21 PM.
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Old 5th August 2012, 07:45 PM   #2168
stewin is offline stewin  Kenya
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hi guys please help this amp works fine with +/-45vlts 8amps with irf540/540n/640n two pairs . they dont even warm when playing loud without a heat sink.

but when using irfp250 /irfb4227 two pairs at +/-60vlts 1amp they get hot in the few seconds of playing. pls help me out guys


artwork and pcb diysmps



thanks in advance

Last edited by stewin; 5th August 2012 at 07:48 PM.
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Old 5th August 2012, 10:28 PM   #2169
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Quote:
Originally Posted by stewin View Post
thanks Whortless i,ll try bc327 and bc337 do they meet the requirements?
It depends on what speed and current (Cg) you will work. BC639/640 seems better.
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Old 6th August 2012, 04:24 AM   #2170
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Originally Posted by paskal9 View Post
have u built it? there's even some difference between the schematic and the pcb. but the most problematic is the cd4049 pinout which is totally different from the datasheet and schematic compared to the pcb. the pcb shouldn't work, but i wonder if anyone did manage to.

can you post some photo so we can see what, where is the problem

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