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F4 power amplifier
F4 power amplifier
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Old 2nd January 2018, 10:25 AM   #4301
marconi118 is offline marconi118  Germany
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And with 2sk1058?
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Old 2nd January 2018, 11:12 AM   #4302
2 picoDumbs is offline 2 picoDumbs  Australia
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With laterals you need to use TL431 with 1.25V reference (not the 2,5V reference version)

Personally if it were me using laterals I would use 4 pairs not 2 and Increase bias to around 1.6A to 2A.
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Old 2nd January 2018, 05:14 PM   #4303
marconi118 is offline marconi118  Germany
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Why in a f5 the laterals can take 1A per pair but in f4 you need 3 pairs for 1A total? Can't I build the f4 with 1 pair and bias it to 1A maybe reducing psu voltage I need only 5w output
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Old 2nd January 2018, 06:45 PM   #4304
2 picoDumbs is offline 2 picoDumbs  Australia
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F5 has feedback
F4 does not have feedback.
Laterals have lower transconductance values.

If you want similar performance specs ( mostly damping factor) it takes more mosfet pairs.
You can throw a single pair in there if you want.
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Old 2nd January 2018, 06:57 PM   #4305
marconi118 is offline marconi118  Germany
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Yes damping factor without feedback is lower.
But unity gain flower has higher damping as the equivalent no feedback f5?
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Old 2nd January 2018, 07:03 PM   #4306
2 picoDumbs is offline 2 picoDumbs  Australia
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Not sure why are you asking about a hypothetical zero feedback F5?

Source follower is a better conguration if you don't need voltage gain.
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Old 2nd January 2018, 07:19 PM   #4307
marconi118 is offline marconi118  Germany
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Pass M2 is also a unity gain buffer stage but with only one mosfet pair...
My previous post question was:
Will an f4 with one output pair havea better damping factor than an hypothetical f5 with zero feedback?

Another question, I will use the TL431 bias schema of the ba1 buffer, can i omit source resistors? With laterals it is convenient as the source is connected on the case, no need to use mica insulator, the heats ink will be the output
In any case thanks for the helpfull answers, I am quite new in Amp building
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Old 2nd January 2018, 07:23 PM   #4308
Zen Mod is offline Zen Mod  Serbia
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F4 power amplifier
F5 sans feedback is pretty high gain thingie , so you can't compare left sneaker and right boot

yes , with TL431 you can skip source resistors , but only with laterals , due to their thermal behavior

verticals will go poof! in most cases
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Old 2nd January 2018, 07:27 PM   #4309
2 picoDumbs is offline 2 picoDumbs  Australia
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F5 is not source follower.
The drain resistance is almost always higher than source resistance speaking from my limited experience.

So source follower will have better damping.

But a single lateral pair will not have better damping than M2 output stage using the original devices.
The transconductance of laterals are much lower.
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Old 2nd January 2018, 07:35 PM   #4310
2 picoDumbs is offline 2 picoDumbs  Australia
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You can omit source resistors.
I already answered that question.

You can also do it with irfp devices using tl431 but it takes more careful and thoughtful planning. Not recommended for new builder.

Laterals are easy.
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