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Old 22nd September 2010, 05:37 PM   #1
Krisfr is offline Krisfr  United States
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Default Power Amp Transistor Pairs

Does anyone have a list or spreadsheet of Power Transistors for POWER AMPLIFIERS?

Or is there a place on the web to find what are MATCHED pairs and what their ratings are?

Like MJ15003 and MJ15004

MOSFETs too...

Thanks
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Old 22nd September 2010, 05:50 PM   #2
wahab is offline wahab  Algeria
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bipolar (bjt) transistor families for audio power output stages
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Old 22nd September 2010, 11:04 PM   #3
AndrewT is offline AndrewT  Scotland
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The complementary is often stated in the Datasheet.
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Old 22nd September 2010, 11:09 PM   #4
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MOSFETs too...

Thanks
IRFP240 and IRFP9240.
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Old 23rd September 2010, 12:32 AM   #5
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IRF240 and IRFP9240???

Have you ever looked at those on a curve tracer? They are not even close. Sounds like something you must have read about in some magazine article or something.
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Old 23rd September 2010, 12:33 AM   #6
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IRF240 and IRFP9240???

Have you ever looked at those on a curve tracer? They are not even close. Sounds like something you must have read about in some magazine article or something.
They dont need to be close.
Feedback sorts out any differences.

I use them in my amps and get great results.

There are loads of amps arounbd using them, they are often pushed on here.
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Last edited by nigelwright7557; 23rd September 2010 at 12:36 AM.
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Old 23rd September 2010, 12:58 AM   #7
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OK, then. I guess the answer to the original question is that it doesn't matter if the transistors are complementary because feedback will fix everything up.
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Old 23rd September 2010, 12:59 AM   #8
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OK, then. I guess the answer to the original question is that it doesn't matter if the transistors are complementary because feedback will fix everything up.
Within reason.

The IRFP9240 was made to be a complement of the IRFP240.
Clearly P channel is much more difficult to make and some compromises had to be made.
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Old 23rd September 2010, 01:01 AM   #9
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Output Transistors
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Old 23rd September 2010, 01:55 AM   #10
CBS240 is offline CBS240  United States
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Quote:
Originally Posted by nigelwright7557 View Post
They dont need to be close.
Feedback sorts out any differences.
The degree of 'correction' depends on what type of loop scheme is employed with that task. Just a plain ol' global fb loop can be overwhelmed by the high frequency distortion components that are related to the non-linear capacitances within a mosfet and may require extra compensation, chipping away at bandwidth...... Feedback does not 'cancel' distortion but can shift it to a higher order of lesser magnitude. If a local loop is tasked with sorting out the differences and is short and fast, much faster than the global loop, the GFB loop will see a much more linear situation, which will make it a lot happier.

I actually use some of the most non-linear mosfets that could be used (cheap planer 'Q-fet' type switching FETs from Farichild), just out of curiosity to see how they could be made to work, but mostly because they have the same trans-conductance, which is the more important issue when using complementary source following mosfets. But with a very fast feedback/feedforward error amplified driver network those non-linear components do not make their way back to the 'global' loop. The result is a very linear, low distortion amplifier.....with higher BW and SR, better SOA than bipolars, and a kick-a$s damping factor. This is something the typical single GFB loop LIN topology, designed for BJT's, just won't do if one simply substitutes these mosfets in for the BJT's.
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