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Registered Member #989
Joined: Sat Sept 08 2007, 02:15AM
Location: São Paulo, Brazil
Posts: 476
I was searching on the internet for some audio amplifier schematics and I found that stupid high power amplifier: It will this work good? I am planning to make it with only 8 IRFP250 and +80V
As the simplicity of the amplifier schematic, I think it will be a very poor quality, and it uses mosfets, and as far I know BJT is better for audio amplifiers.
Registered Member #1774
Joined: Wed Oct 22 2008, 02:51AM
Location:
Posts: 135
Im not certain but I heard that Mosfets are better. Im just curious though, what do you need such a high power amp for? at 8ohms thats like 800watts! Ive never seen a speaker rated that high (In RMS)
Registered Member #509
Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329
There are highly linear audio mosfets... but they certainly arent IRFP250s is an article on a high power amp, and gives a bit more information on using mosfets. A lot of other good articles/projects/information on audio equipment on the website, if you havent browsed it allready.
Registered Member #989
Joined: Sat Sept 08 2007, 02:15AM
Location: São Paulo, Brazil
Posts: 476
I dont need 7800W rms :P that is what I will reduce the circuit. The mosfets are better for reduce the loses, because in some currents, they dissipate less heat (so less consumition [i])
Registered Member #509
Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329
A device operating in a linear fashion is still going to dissipate the same amount of power.
If you have + and - 30 volt supplies, and are outputing 8 volts to an 8 ohm load, 1 amp will be drawn, and the remaining 22 volts(@1 amp, so therefore 22W) will be dissipated in the transistor.
A BJT will have a base current that it will have to dissipate, but a Mosfet amp will have an increased bias current too.
Mosfets only make for lower dissipation when used as switching devices, so if youre making a Class D amp, Then you definitely want to use mosfets.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Mestre Racerxdl wrote ...
I dont need 7800W rms :P that is what I will reduce the circuit. The mosfets are better for reduce the loses, because in some currents, they dissipate less heat (so less consumition (I think the word is wrong :P))
They dissipate the same amount of heat for a given power output, speaker and supply voltage.
Registered Member #1819
Joined: Thu Nov 20 2008, 04:05PM
Location:
Posts: 137
El_Roberto wrote ...
Im not certain but I heard that Mosfets are better.
MOSFETs are only better if used correctly; this means a very high power driving circuit to overcome the MOSFETs' gate capacitances. The main advantage with using them is that they have a positive temperature coefficient, meaning that their resistance goes up as their temperature increases. This stops thermal runaway (but only in a linear circuit).
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Stupid audio amplifier
