If using vertical FETs keep the bias as low as possible to stop thermal runaway. If the bias is just enough to kill crossover distortion you probably wont even need any thermal feedback to the bias cct.
I have built about 40 amps of a similar design and all have run very well.
I think we have a 100 threads about this circuit - does anyone have an idea how to stop it popping out every month or so...
Yes, it will work and survive with 20mA bias and really big heatsink but it sounds awful - LM3886 is a State of the Art class compared to that missgeburt
LM3886 better than that amplifier?
How?
LM3886 better than that amplifier?
How?
Easy...
Almost everything is better than that insult of an amplifier.
When I was 3 years old I didn't believe my dad that hot stove is not to be touched, I learned it a hard way - although those glowing circles looked so attractive...
Now, now .... the LM3886, 3875, 4780's et alia in many configurations sound very fine.
I recommend you IRF640/9640 pair, for some reason, it won't run thermally! I said this a couple of times, I made it overheat with excesive quiescent current, played as guitar amp for about 3 or 4 hours at max and survived! And its heatsink it's not big enough... It will sound without co distortion even with trimpot at 0 ohm...
The designer says quiescent current should be 100 mA...
My personal opinion? This amp do sound great! It's simple, and it doesn't fail. Last Friday worked really great with at my band's show.
Hi,
I am not too familiar with those theories of you guys. I just follow blindly. But I tried his 'page2' project and it was great. I will try this one too next month and see how it works. Just in case you guys want to know where it comes from :
60 Watt MosFet Audio Amplifier - RED - Page100
If you have a smaller stomach, try this :
25 Watt MosFet Audio Amplifier - RED - Page2
which you cannot failed. It is playing 'Hotel California' on my rack as we speak. I had some boards for this (page2). Call me if you don't want your hands dirty :
tony_chan_cf@email.com
I am not too familiar with those theories of you guys. I just follow blindly. But I tried his 'page2' project and it was great. I will try this one too next month and see how it works. Just in case you guys want to know where it comes from :
60 Watt MosFet Audio Amplifier - RED - Page100
If you have a smaller stomach, try this :
25 Watt MosFet Audio Amplifier - RED - Page2
which you cannot failed. It is playing 'Hotel California' on my rack as we speak. I had some boards for this (page2). Call me if you don't want your hands dirty :
tony_chan_cf@email.com
Redcircuits tells the quiescent current must be around 130mA, so this is way to high?=>20mA
Can someone answer me the question about the lateral/vertical thing. I have never heard about it.
I also did a simulation in "Multisim" and it works just fine. But a simulation is never the real thing distortion, heat,..
Can someone answer me the question about the lateral/vertical thing. I have never heard about it.
I also did a simulation in "Multisim" and it works just fine. But a simulation is never the real thing
distortion, heat,..Vertical FETs have a near zero temperature coef around Id=6A to 15A.
Look at the graph of Vgs vs Id with two or more temperature plots.
Lateral FETs have a near zero temperature coef around 100mA.
Again look at the Vgs vs Id graphs.
The Lateral FET outputs can manage with no temperature compensation for the output idle (bias) current since they pass less current as the temperature rises, whereas Vertical FET output increase the idle current as temperature rises until they reach the current around which they stabilise. Before they reach this 6A to 15A stable current region they have severely oveheated and gone PoP. Vertical FETs must have a temperature compensation built into the idle and operating current to ensure that they do not suffer from Thermal Runaway.
Look at the graph of Vgs vs Id with two or more temperature plots.
Lateral FETs have a near zero temperature coef around 100mA.
Again look at the Vgs vs Id graphs.
The Lateral FET outputs can manage with no temperature compensation for the output idle (bias) current since they pass less current as the temperature rises, whereas Vertical FET output increase the idle current as temperature rises until they reach the current around which they stabilise. Before they reach this 6A to 15A stable current region they have severely oveheated and gone PoP. Vertical FETs must have a temperature compensation built into the idle and operating current to ensure that they do not suffer from Thermal Runaway.
Juma what language is that mis.... word of yours, I speak some dutch and that word makes a lot of sense to me regarding that circuit
Maybe it can be made to work on such a low bias but its not optimal, I wouldnt use those mosfets without temperature compensation.
There is another member here that showed another design also running these mosfets without T comp and he uses these amps for PA so it must be workable though.
I would rather get two lateral mosfets to use with this circuit, there are laterals on the market now that arent that expensive.
Maybe it can be made to work on such a low bias but its not optimal, I wouldnt use those mosfets without temperature compensation.
There is another member here that showed another design also running these mosfets without T comp and he uses these amps for PA so it must be workable though.
I would rather get two lateral mosfets to use with this circuit, there are laterals on the market now that arent that expensive.
dict.cc dictionary :: Missgeburt :: German-English translation
BTW, slideman82 says that he used that... that device as a guitar amp. I think it's a proper use for it. It's definitely not sutiable for hi-fi...
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