Just wondering how to design a source follower output stage. (Class A SE) with a resistor as the load and not a CCS?
I understand that it would be extremely inefficient.
Looking for about 10W into 8ohms. Probably cap couple to load.
1.5A bias current or so.
Thanks for any help or any links to how to work out the values i need.
I understand that it would be extremely inefficient.
Looking for about 10W into 8ohms. Probably cap couple to load.
1.5A bias current or so.
Thanks for any help or any links to how to work out the values i need.
It takes a lot. For 10 Watt.
10 Watt is SQR(10*16) = 12.65 Volt peak
Most effective would one 8 Ohm power resistor.
Supply need to be more than 3x12.65V. Probably 42VDC.
Current needs to be more than 3.16A Say 3.40A.
Across power resistor would be ~27-28 Volt
27V x 3.40A = 91.8 Watt 8 Ohm resistor.
You could use 4 resistors 8.2 Ohm
Each should be rated more than 25 WAtt
You can see in my simulation how one could do.
10 Watt is SQR(10*16) = 12.65 Volt peak
Most effective would one 8 Ohm power resistor.
Supply need to be more than 3x12.65V. Probably 42VDC.
Current needs to be more than 3.16A Say 3.40A.
Across power resistor would be ~27-28 Volt
27V x 3.40A = 91.8 Watt 8 Ohm resistor.
You could use 4 resistors 8.2 Ohm
Each should be rated more than 25 WAtt
You can see in my simulation how one could do.
Attachments
would it be easier to do as a BJT or a Mosfet?
I was thinking mosfet.. as an example a IRF240N or something.
Like i said i dont care how inneficient it is.. just 10W 8 ohms and nice gradual clipping etc.
Thanks!
I was thinking mosfet.. as an example a IRF240N or something.
Like i said i dont care how inneficient it is.. just 10W 8 ohms and nice gradual clipping etc.
Thanks!
i did some sim and i came up with
45vdc supply. 8 ohm resistor for load. 3.75A bias
using IRF240
can get about 14v peak into 8 ohm load at clipping.
12v peak into 4 ohm load at clipping.
can u confirm this?
ends up being like 35v bias for the 30v drop across the 8ohm resistor load.
hope that makes sense. lol.
45vdc supply. 8 ohm resistor for load. 3.75A bias
using IRF240
can get about 14v peak into 8 ohm load at clipping.
12v peak into 4 ohm load at clipping.
can u confirm this?
ends up being like 35v bias for the 30v drop across the 8ohm resistor load.
hope that makes sense. lol.
Yes.
All the figures make sense.
But it must a h**l of a power resistor.
30v x 3.75 = xxxx Watt !!!!!
But if you have 4 power resistors rated 50 Watt each
then you can use those four 8 Ohm resistors together.
Difference by using MOSFET or BJT.
Both can be used.
But we get more dropout voltage with MOSFET
0.7Volt and 4v is a difference 3.3v in favour of BJT
So teoretically MOSFET need at least 3.3v higher power supply.
All the figures make sense.
But it must a h**l of a power resistor.
30v x 3.75 = xxxx Watt !!!!!
But if you have 4 power resistors rated 50 Watt each
then you can use those four 8 Ohm resistors together.
Difference by using MOSFET or BJT.
Both can be used.
But we get more dropout voltage with MOSFET
0.7Volt and 4v is a difference 3.3v in favour of BJT
So teoretically MOSFET need at least 3.3v higher power supply.
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This would be my first choice for what you have in mind:
http://www.diyaudio.com/forums/pass-labs/66822-sewa-seven-watt-amplifier.html
http://www.diyaudio.com/forums/pass-labs/66822-sewa-seven-watt-amplifier.html
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