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Old 27th August 2014, 12:11 PM   #1
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Default Mosfets for amplifier

Hi, i'm new in eletronics world and i'm trying to build a class A amplifier mosfet. I found many great projecrs but i didn't found the needed fets. Can someone give a list o all mosfets that can be used in good amplifiers and theach how to build one from zero? Thank a lot
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Old 29th August 2014, 12:02 AM   #2
JMFahey is offline JMFahey  Argentina
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Sorry but your question is too generic.
Post a project you are interested in so we see which Mosfet is used.
I suggest you choose one already posted in this Forum and built by many, so you can see how they built them and where they sourced the materials.
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Old 29th August 2014, 10:25 PM   #3
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hi, sorry about insist but, what i want to know is the fets that can be used in audio amps, because its not every fet that can be used for this. its because where i live have just too few mosfets for sale, and if i know wich ones can be used and how to build the amplifier i could get somewhere :P

thanks
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Old 30th August 2014, 01:46 AM   #4
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Some FETs are better suited for switching application's, this is true.

But all FET's can be used in a analog circuit as well.

A engineer from TI explained that to me once when I asked him a similar question.

The First place to start is to learn how FET's work as compared to Bipolar Junction transistors (BJT's) and their differences.

FWIW

jer
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Old 30th August 2014, 02:02 AM   #5
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Ooh, now i get it. Thanks and, do you have any invices about learning to project amplifiers?
Thanks. See ya
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Old 30th August 2014, 02:54 AM   #6
bimo is offline bimo  Indonesia
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Quote:
Originally Posted by lincoln rogala moro View Post
hi, sorry about insist but, what i want to know is the fets that can be used in audio amps, because its not every fet that can be used for this. its because where i live have just too few mosfets for sale, and if i know wich ones can be used and how to build the amplifier i could get somewhere :P

thanks
If you replace BJT with mosfet with minor modification to get "just work" then you will conclude that mosfet is not good for audio amp.
Mosfet have different character (ex. high input impedance, high input capacitance, etc) than BJT, and the circuit/schematic to use them must optimize by its character to get low THD, high slew rate, etc.
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Old 30th August 2014, 05:56 AM   #7
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by lincoln rogala moro View Post
i'm trying to build a class A amplifier mosfet. Can someone give a list o all mosfets that can be used in good amplifiers
Sorry, it does not work that way.

Quote:
I found many great projecrs but i didn't found the needed fets.
That´s better.
Link some project you liked, then mabe we can suggest some replacement.

Quote:
and theach how to build one from zero?
Mmmmmhhhhh, not that easy.
If inexperienced, first learn basic Electronics, how to solder, how to measure with a multimeter and start by building some simple projects.
Step by step.

EDIT: and tell us where you are from, so we can suggest suppliers.
Can you buy from EBay or USA suppliers such as Mouser or Digikey?

Last edited by JMFahey; 30th August 2014 at 05:58 AM.
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Old 30th August 2014, 11:14 AM   #8
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I know a few things of eletronic, bjt its just a little bit. I will learn the basics. Well i had to format my pc so i lost the projects, but one i would like to build is this
DIY Class-A 2SK1058 MOSFET Amplifier Project
But i didn't found the fet to buy in my country. I live in Brazil. There's another fet that can be used?
Thank you very much
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Old 30th August 2014, 11:39 AM   #9
Mooly is offline Mooly  United Kingdom
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BUZ900, EC10N16, EC10N20. You could probably use the dual die versions of all these with little detriment (16 amp devices... they will have a higher gate capacitance)
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Old 30th August 2014, 12:43 PM   #10
JMFahey is offline JMFahey  Argentina
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Just checked , no lateral/audio MosFets available in Brazil.
Only vertical/switching/HexFets .
But you can search for those suggested by Mooly, which are equivalent to the old Hitachi/Toshiba 2SK and buy them in USA or England with your Credit Card.
Small packages have no Customs/Alfândega problems because you pay no taxes on less than 50U$ purchases.

As a side note, just to practice, build that circuit with a *switching* type Mosfet, say an IRFP240 or 250 which costs around 6 R$ in São Paulo.
It *will* work, remember to bias it to 12V on its source with 24V power supply.
Switchers are reasonably linear at high currents and yours uses 12V into 15 ohms which is almost 1 Ampere.

Not the original but it will not sound bad.

And when you get the original MosFet, replace it.
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