MOSFET Amplifier IRFP240/IRFP9240

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#24
an amplifier that its designed to work with V limmiters in a PA housing with controled ventilation might escape the smoke even if bias is unstable

it might looks thermally unstable as a circuit but it might be stable enough as a complete product ....

Let us not forget that even that even pro amps like QSC dont use a transistor to monitor temperature .... just a simple noisy inexpensive thermistor ...still the get away with it ....

And by the way i also agree on the bias issues and also to my understanding there is no chance that an amplifier like that will keep stable without a zobel, with inductor,and clamp diodes that is missing from your schmtics and pcb ....unless all the above is located else where

Bottom line is if you invest money in a PA or any other big amplifier construction ( since amplifiers like that tent to cost some money ) it would be wise to have all mistakes corrected and use state of the art circuit and semis any way....
 
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#25
Why anyone have no any coment on unusuall circuit Q8,Q9,R17,R21 and Q7,Q10,R18,R22 in voltage amp... Mosfets IRFP240 and IRFP9240 had integrited clamp diode, R50, C11 are zobel, and inductor is on speakers terminal. On the fotos you can see an amp without fan, make for home listening many years ago. Amp is simple to build and test, work with two output mosfets on +/-50V DC.
 
#26
Apexaudio, thanks for sharing, but I think if you expected to come here, put your design on display (and perhaps sell some PCBs) and get universal praise for your design and think that because it has been in use for 10 years that it cant be improved on, you are mistaken. these guys are not criticizing, they are bouncing ideas to improve the circuit around. there are some serious pros here, in general the attitude here is a proactive one, no need to be defensive. if you dont want constructive criticism, I have to wonder why you posted...... take it on board; or not. up to you
 
#27
In last tree years in my PA amplifiers I use new design with 2SA1943/2SC5200 bipolar output tranzistors and IRF2807 mosfets for step. Amplifier work in H class 0,+/-60V,+/-120V.
 

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#34
qusp said:
if you expected to come here, put your design on display (and perhaps sell some PCBs) and get universal praise
Click to expand...

He gave us more than sufficient info (including the PCB layout) to DIY.
I don't see the problem if he sells some boards to those short on time.
I also don't see a problem with universal praise for openly sharing the
design of a commercial product.
 
#35
arrrghh, i'm not knocking him for anything but the seemingly shirty tone with which he replied to some suggestions for improvements. I dont see a problem with selling the PCBs either. I dont have a problem with any of it except getting short with people who are just doing what people do when a design is posted here. and even that I dont really have a problem with, but I did think it worth a mention
 
#36
qusp said:
arrrghh, i'm not knocking him for anything but the seemingly shirty tone with which he replied to some suggestions for improvements. I dont see a problem with selling the PCBs either. I dont have a problem with any of it except getting short with people who are just doing what people do when a design is posted here. and even that I dont really have a problem with, but I did think it worth a mention
Click to expand...
Sory, I dont speak English, is hard to me to replied becouse I dont understend question or sugest sometimes, I hope my tone will be beter in future.
 
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