Lumba Ogir said:
Lumba,
lateral MOSFETs have an equivalent fT in the 100MHz range, as mentioned.
Vertical MOSFETs manage about three times as much, around 300MHz equivalent.
Which fairly corresponds with the ratios of the switching and rise times of both MOSFET types.
There's not an fT with MOSFETs, as there's no hFe, equivalent fT for a MOSFET is derived by Gm/(2*Pi*Cgs)
Once you found your brain in your private tete-a-tete at the HA-larious Colangelo thread, do try a search for a sense of humor.
Hi guys,
This speed thing ! My maths is useless, so if what I am saying is a load of tripe please do say so
The gate is seen as a capacitance. To swing say 10 volts in 180nS ( This is max on time from the data sheet under specific conditions and I just picked this as a value to work with) equates to 55 volts per microsecond. If the capacitance is 1 nF that means a current source is needed that will supply 55 mA current to give that rate of change of voltage on the gate. That takes some doing at that speed.
Does that sound reasonable or have I lost the plot already
There has to be more to it than this though because if this were the only requirement then why does the off time not equal the on time-- 60 nS is all that is needed to turn it off. Charging and discharging a cap is "symmetrical" time wise. As the FET does not suffer from hole storage effects like the Bjt what causes this effect ?
This speed thing ! My maths is useless, so if what I am saying is a load of tripe please do say so
The gate is seen as a capacitance. To swing say 10 volts in 180nS ( This is max on time from the data sheet under specific conditions and I just picked this as a value to work with) equates to 55 volts per microsecond. If the capacitance is 1 nF that means a current source is needed that will supply 55 mA current to give that rate of change of voltage on the gate. That takes some doing at that speed.
Does that sound reasonable or have I lost the plot already
There has to be more to it than this though because if this were the only requirement then why does the off time not equal the on time-- 60 nS is all that is needed to turn it off. Charging and discharging a cap is "symmetrical" time wise. As the FET does not suffer from hole storage effects like the Bjt what causes this effect ?
Hello Nigel,
I do understand what you are saying about ground planes, and it will give a lower overall impedance which is very beneficial in many applications, but with audio the devil is in the detail as far as where the best points to return various components to are.
It's a bit like with the feedback take off point mentioned earlier, there was plenty of copper there, but if you connected a 'scope to that print and could move the probe around it the signal would be constantly changing. We tend to think of copper as zero ohms but it's anything but. If the board is double sided there is also the possibilty of the ground plane effecting the circuit due to capacitive coupling between the two halves.
No easy answer and there is no right and wrong way, both have advantages and disadvantages.
Regards Karl
I do understand what you are saying about ground planes, and it will give a lower overall impedance which is very beneficial in many applications, but with audio the devil is in the detail as far as where the best points to return various components to are.
It's a bit like with the feedback take off point mentioned earlier, there was plenty of copper there, but if you connected a 'scope to that print and could move the probe around it the signal would be constantly changing. We tend to think of copper as zero ohms but it's anything but. If the board is double sided there is also the possibilty of the ground plane effecting the circuit due to capacitive coupling between the two halves.
No easy answer and there is no right and wrong way, both have advantages and disadvantages.
Regards Karl
Jacco,
please read and learn
http://www.diyaudio.com/forums/showthread.php?s=&threadid=109229&highlight=
please read and learn
http://www.diyaudio.com/forums/showthread.php?s=&threadid=109229&highlight=
Per-Anders is an EE and has been building lateral MOSFET output stages for +2 decades.
Yet he speaks little, as so often, and asks you instead of talking a great deal.
What does that tell you : a sign of ignorance, or a modest display of intelligence ?
You claimed that the extreme high speed of Lateral MOSFETs is part of the reason for them being THE superior audio output devices, yet Vertical MOSFETs are so much faster.
What really sets Lateral MOSFETs apart from Verticals is their very awkward transconductance behaviour at high frequencies, stuff that has also been posted here several years ago.(eg jcx, i think)
Something you did not mention in your very antique smelling Pain serenade, antique as in "heard it all 20 years ago".
You seem to enjoy to talk a lot but rarely care to listen, still an abundance of young buck hormones i guess, old folks like P-A and me unfortunately lost them somewhere along the trail.
Yet he speaks little, as so often, and asks you instead of talking a great deal.
What does that tell you : a sign of ignorance, or a modest display of intelligence ?
You claimed that the extreme high speed of Lateral MOSFETs is part of the reason for them being THE superior audio output devices, yet Vertical MOSFETs are so much faster.
What really sets Lateral MOSFETs apart from Verticals is their very awkward transconductance behaviour at high frequencies, stuff that has also been posted here several years ago.(eg jcx, i think)
Something you did not mention in your very antique smelling Pain serenade, antique as in "heard it all 20 years ago".
You seem to enjoy to talk a lot but rarely care to listen, still an abundance of young buck hormones i guess, old folks like P-A and me unfortunately lost them somewhere along the trail.
Lumba Ogir said:
It's a rather unusual claim to say that laterals are faster than verticals and since I work as an design engineer where I have heard the opposite I would very much like to hear some evidence of your claim.
Even the heavy dude Bob Cordell says this:
"The drain-gate capacitance of verticals is not a big problem if the right kind of drivers are used. Verticals are fundamentally much faster than laterals in terms of equivalant ft."
http://www.diyaudio.com/forums/showthread.php?postid=1536554#post1536554
hi mooly,
finally my parts has arives. should i follow your first posted circuit deisgn?
tell you one joke, Today i just tried to make class a simple circuit just for fun, using 2sk1058, the sound quality i really didin't like it, thou it was single ended class A amp. i want to ask you one question, does class A amp sound really good? honestly tells you i never heard class A amp sound ecpt mine ugly. i know yours is not class A. i will make one class A amp after i finish yours. i am thinking to make aleph-x...still far far away....ha.ha...have to learn more right...
Best regards
michael
finally my parts has arives. should i follow your first posted circuit deisgn?
tell you one joke, Today i just tried to make class a simple circuit just for fun, using 2sk1058, the sound quality i really didin't like it, thou it was single ended class A amp. i want to ask you one question, does class A amp sound really good? honestly tells you i never heard class A amp sound ecpt mine ugly. i know yours is not class A. i will make one class A amp after i finish yours. i am thinking to make aleph-x...still far far away....ha.ha...have to learn more right...
Best regards
michael
hi nigelwright7557,
i don't know the sound comming distorted like a bit humm....
sound not sweet and sharp at all...its like clean but not sweet...so i didn't like it.
the voltage was right and one resister gets very hot. transistor is ok...
so i was thinkign may be i am still not that level yet for making class A amp...right now...
Hi mooly,
sorry, need to ask you for parts list cause i need to know those resister watts and diod too....
thank you.
michael.
i don't know the sound comming distorted like a bit humm....
sound not sweet and sharp at all...its like clean but not sweet...so i didn't like it.
the voltage was right and one resister gets very hot. transistor is ok...
so i was thinkign may be i am still not that level yet for making class A amp...right now...
Hi mooly,
sorry, need to ask you for parts list cause i need to know those resister watts and diod too....
thank you.
michael.
Hi Space,
All 0.6 watt metal film apart from all the 0.22 ohms which are 3 watt types, and these must be non inductive-- no wirewounds-- try and get the cermet or film types, and the 10 ohm in the Zobel network which is a 2 watt carbon type. Unless you plan on testing at high powers and at high frequencies 2 watt is fine. The only diode is the 12 volt zener and any 0.4 or 1.3 watt type is fine.
Build it exactly as per the circuit to begin with. If you need any advice or help just ask
When it's nearly done let me know and I will post how to test it so if there are any problems or errors it won't pop the outputs.
Use a preset for R8 at first.
All 0.6 watt metal film apart from all the 0.22 ohms which are 3 watt types, and these must be non inductive-- no wirewounds-- try and get the cermet or film types, and the 10 ohm in the Zobel network which is a 2 watt carbon type. Unless you plan on testing at high powers and at high frequencies 2 watt is fine. The only diode is the 12 volt zener and any 0.4 or 1.3 watt type is fine.
Build it exactly as per the circuit to begin with. If you need any advice or help just ask
When it's nearly done let me know and I will post how to test it so if there are any problems or errors it won't pop the outputs.
Use a preset for R8 at first.
hi mooly,
ok i will follow the same. as i have seen your amp need 45vdc, i have one transformer is 4amp 22-0-22v ac....do you think it should be right for this amp?....after dc will be about 32 to 36 vdc right? otherwise i have another one is 56v after dc arround 10amp.
what is the min and max voltage can be apply on it?
can i have a fresh circuit diagram? i saw yours is distorted image can't see clearly. you can post me to my email?....."mitoo_singapore@yahoo.com"
tomorrow i will go for buying some parts. thank you for help.
best regards
michael
ok i will follow the same. as i have seen your amp need 45vdc, i have one transformer is 4amp 22-0-22v ac....do you think it should be right for this amp?....after dc will be about 32 to 36 vdc right? otherwise i have another one is 56v after dc arround 10amp.
what is the min and max voltage can be apply on it?
can i have a fresh circuit diagram? i saw yours is distorted image can't see clearly. you can post me to my email?....."mitoo_singapore@yahoo.com"
tomorrow i will go for buying some parts. thank you for help.
best regards
michael
The 22 volt transformer is OK initially, the maximum power output will be reduced, thats all. If you mean -/+ 56 volts DC (112 volts total) from your other transformer then thats a little bit high really.
The smaller one is perfect for initially testing it all, don't go mad with bucket loads of smoothing caps, a pair of 4700 mfd or 6800 are ideal.
The smaller one is perfect for initially testing it all, don't go mad with bucket loads of smoothing caps, a pair of 4700 mfd or 6800 are ideal.
hi mooly,
I tell you my exp on class A today. when i made the class A amp. its like the worst power hungry animal i ever seen. Always hungry for power supply, suck all power from transformer even want to eat my transformer too. It was working but not at that level.
the amp is here......
http://diyaudioprojects.com/Solid/ZCA/ZCA.htm
molly, you send me the circuit design is not clear at all...some wordings can't read properly. pls check the email...
thank you.
mchael
I tell you my exp on class A today. when i made the class A amp. its like the worst power hungry animal i ever seen. Always hungry for power supply, suck all power from transformer even want to eat my transformer too. It was working but not at that level.
the amp is here......
http://diyaudioprojects.com/Solid/ZCA/ZCA.htm
molly, you send me the circuit design is not clear at all...some wordings can't read properly. pls check the email...
thank you.
mchael
True single ended Class A -- which it sounds like you were playing with is very inneficient. The only advantage of Class A is in eliminating crossover distortion, but it is still prone to all the other problems that affect other classes. Class A in itself is no guarantee of good sound quality or technical quality come to that.
It's how it's implemented that counts.
It's how it's implemented that counts.