NVMOS amplifier

[kASD]

Hi Workhorse
greetings which is the most suitable mosfet for this amp
IRF 250 IRF260 IRF460 for best results nice to see this thread moving
warm regards
andrew lebon

IRF460 is good candidate

 

[kASD]

Hello Workhorse Sir
greetings i am a new member of diy audio i would like to make this
amplifier little confused which schematic to refer to i can make a simple pcb for it only
need little guidance please can you help me as this is my first project in electronics ONLY please tell me wich circuit post to follow
warm regards
sameer x1

Sameer,
If this is your first electronics project then i will advice you not to build this one, take something simpler with transistors as your project.

 

[sdman]

Bias Current

Workhorse, what's the nominal bias current of the nvmos amp using the IRFP250s?
Just a thought on the PC board, do you think the signal grounds should be seperate from the power ground?

Sam

 

[andrewlebon]

pcb please

Hi Alex mm
greetings any update on pcb can you share pcb so i can try it
workhorse amps are special
warm regards
andrew lebon😎😎

 

[kASD]

Workhorse, what's the nominal bias current of the nvmos amp using the IRFP250s?
Just a thought on the PC board, do you think the signal grounds should be seperate from the power ground?

Sam

Nominal bias for IRFP250's is 30mA.

Regarding the grounds, no issue in that, as long as signal return path is kept minimum.

 

[vedmitraa]

Hi Alex mm
greetings sir any update on pcb can you share pcb so i can try it
I have a huge collection of IRFP460.and I want to use them.with love from city of Tajmahal
Vedmitrasharma.

 

[vedmitraa]

Hi Alex mm
greetings again sir,two days and no reply. any chance to use my stock of 460.any chance of p.c.b.

 

[vedmitraa]

Hi Alex mm
greetings again sir,two days and no reply. any chance to use my stock of 460.any chance of p.c.b.

 

[alex mm]

PCB NVMOS .....

..... ok right now .....🙂 I have not only diy work to do , so you must be patient 🙄
Regards Alex.

 

[vedmitraa]

Thanks a ton sir,
a silly question can more outputs be added to this circuit.If possible how many and what will be the value of gate resistances and' s' resistance.thanks again

 

[kASD]

Schematic has been updated to facilitate more devices and better stability and ease in setup. 🙂

Some last minute changes include better positioning for compensation capacitors, some values have been optimized along with part numbers and some additional components have been added.

Kanwar

 

[kASD]

Thanks a ton sir,
a silly question can more outputs be added to this circuit.If possible how many and what will be the value of gate resistances and' s' resistance.thanks again

You can parallel upto 6 pairs of mosfets. Gate resistors and Source resistors will remain of same value. Only thing you need is to put a 1N4148 diode in anti-parallel to each gate resistor in order to allow fast discharge and thus decreasing cross conduction at HF.

 

[sdman]

Updated

Just making sure, a diode across the 220 ohm gate resistors?
Are the BC546 and 556 a better transistor than the MPSAs?

thanks, sam

 

[kASD]

Just making sure, a diode across the 220 ohm gate resistors?
Are the BC546 and 556 a better transistor than the MPSAs?

thanks, sam

BC546/556 have higher gain than MPSAs. I have used MPSAs in cascode form where high voltage level shifting takes place. Regarding gate//diode, see the attached pic for clarification 🙂

 

[sdman]

THe BC556Bs are lower voltages than the MPSAs,will that be a problem?

sam

 

[kASD]

THe BC556Bs are lower voltages than the MPSAs,will that be a problem?

sam

No, they are used at low voltages only well under their ratings.

 

[norazmi]

workhorse, what a minimum voltage for this amp and without any adjustment for the components. let say +35 0 -35 vdc.

 

[vedmitraa]

Thanks Mr. Workhorse, Is there any P.C.B. design for the same.Please publish if there is any.
regards
Vedmitra Sharma

 

[sdman]

Jfet Input

Hello Workhorse,

How difficult would it be to change the input to Jfet like the Goldman?
I think they used the 2N5565 Jfet. They can be found but they are pricey.

sam

 

[kASD]

Try it