Possible for mix IRF + FQA as complementary mosfet? - diyAudio
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Old 18th December 2014, 04:46 AM   #1
pwan is offline pwan  United Kingdom
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Default Possible for mix IRF + FQA as complementary mosfet?

Sorry if this sounds a silly question, but I don't think I've seen one done it yet.

Is it possibility to mix IRF and FQA as complementary mosfet ( e.g. IRF for P channel and FQA for N channel, or vice versa) provided similar transconductance? If not, why.

Thanks in advance.
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Old 18th December 2014, 05:37 AM   #2
Zen Mod is offline Zen Mod  Serbia
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I didn't think about that and didn't tried
take capacitances in account , too

though , in A class source follower , everything is possible
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Old 18th December 2014, 09:15 AM   #3
JBL4435 is offline JBL4435  Germany
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I'm interested in the same issue.

Attached is a quick comparison of the available (except SFP9610) types that could be used as small signal mosfets.

Do I see it the right way when I say FQP3P20 + FQP3N30 are the best (available) complementary pair?
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File Type: jpg IRF_FQP_comparison.jpg (75.6 KB, 74 views)
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Old 18th December 2014, 10:44 AM   #4
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nothing wrong with IRF 610/9610 , either
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Old 18th December 2014, 11:54 AM   #5
pwan is offline pwan  United Kingdom
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Quote:
Originally Posted by Zen Mod View Post
nothing wrong with IRF 610/9610 , either
The story of P-channel ones from IR made me worried.
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Old 18th December 2014, 12:23 PM   #6
Zen Mod is offline Zen Mod  Serbia
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well - you didn't said in which apparatus you are planning to use them
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Old 18th December 2014, 01:03 PM   #7
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This is a good and interesting thread but also very loaded.
As far as I know, there are no more complementary low power mosfets suitable for audio. Toshiba had the last ones and those are only available as NOS. Prakit on the forums has some available last i checked. So this mix n match approach may be the the only potential solution for production parts But to decide the most important parameters to match ain't always obvious.
I'd go for transconductance as THE most important parameter for a push pull stage.

Last edited by kasey197; 18th December 2014 at 01:05 PM. Reason: Added potential n production parts
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Old 18th December 2014, 01:42 PM   #8
pwan is offline pwan  United Kingdom
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Quote:
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well - you didn't said in which apparatus you are planning to use them
F5.

(also, may be other Class AB Hexfet push pull amp.)

In addition what I try to understand is whether or not verticle mosfet P and N channel ( regardless of brands) can be mixed and matched .. based on the gain and Ciss at a particular fixed voltage

Last edited by pwan; 18th December 2014 at 02:03 PM.
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Old 18th December 2014, 02:23 PM   #9
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yes , they can be mixed

additionally - P3 in F5 is your best friend , if you arm your self with THD analyzer , be it real one , or sound card based + adequate software
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Old 18th December 2014, 02:42 PM   #10
pwan is offline pwan  United Kingdom
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yes , they can be mixed

additionally - P3 in F5 is your best friend , if you arm your self with THD analyzer , be it real one , or sound card based + adequate software
Thanks , Zen Mod.

I am now looking on the IRFP240 - P9240 datasheet. Say, at 30V Vgs 4.5V the Id of P240 is ~0.6A while P9240's one is 2A. Very different. I wonder how it actually happening when the working amp..... Solely let the NFB to solve the un-equal gain of both halves?
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