As Zen Mod said, the difference is due to the Enhacement mode device and the depletion mode device characteristics. The Pic you show uses the 'ol standby enhacement mode device. It needs about 4V G-S to turn on to some idle current. The G-D R and the G-Gnd R create a voltage devider which provides about that level at the gate node.
The IXYS Depletion mode device would be on with a few amps flowing through it without any bias at all. The G-D R is not needed. In fact almost no bias voltage at the gate is needed. It just so happens this device will provide a reasonable idle current with the Gate at about Gnd potential. Much like JFETs.
Now I want to ask a question.The 10k R from G-S is a little interesting. I haven't given it enough thought yet obviously but it does more than give the amp an input resistance. It is tied to the Source R which will create some Positive feedback
The source resistance provides some local feedback to linearize the amp. But it also raises the source voltage, so to keep the Vgs at around zero potential for automagically biasing at the right Id, the gate has to be 'lifted up' to the source, hence the 10k.
But the signal at the source is (almost) as high as at the gate so there is very little signal across that 10k so to the input it looks much larger than 10k. This is called 'bootstrapping the input impedance' and it is indeed a form of pos feedback, but not error cancellation.
jd
An Enhancement Mode MOSFET is generally considered to be "Fully Enhanced" or turned on to it's rated Rdson value with 10V Gate - Source. Generally speaking, more than 20V G-S and you are on the edge of breaking down the oxide between the gate and the chanell creating "magic smoke". Very often a zener diode will be seen G-S which protects the device from ever having to much G-S Voltage and blowing up.
It would be considered in the linear mode at around 4V G-S for the IRFP240 and the same for the IXYS part would be at about 0V
Well, I agree here but, not if the 10k is connected above the 1 ohm Source R. Only if the 1 ohm is subjected to Source current and signal with the 10k refrenced to Gnd?
I'm thinking the G-S Voltage will remain close to constant and the Source and Gate will raise and lower with the current change through the Source R.
O.K. Still thinking. I'm used to typical signal levels (+- 1V) causing cliping or something in a circuit like this and maybe without this arangement that might be happening?
all the ones I had added are gone
OK guys,
I love the name DeLite
I love Steve Eddy's bulbs
I think I may have found a better part - I'll let you
know shortly.
good name. also you could use "Enlightenment" or "Sunrise"
......
I think I may have found a better part - I'll let you
know shortly.
Papa ....... I think that's time to put this line in your sig :
"allowed for all spoiled kids , but not for faint in heart ones "
actual GB isn't even started properly ..... and you are announcing better part .....
Better to change mind on part now, than after the order is placed.
I am assume the better part is the D-Mosfet, since there are not too many other parts. Unless of course, papa is talking about the
.Those don't seem easy to find in hardware store either.
You will have to forgive the occasional lapse.
I have a purchasing manager, a big budget, and indulgent
business partners, so I don't think twice about ordering up
two different types of parts, or even the antique light bulbs.
That entices me to forget that not everyone is so blessed.
On the other hand, somebody needs to do it, if only to
provide vicarious entertainment. A little adventure won't
hurt you at 5% of the price of audiophile interconnects.
I have a purchasing manager, a big budget, and indulgent
business partners, so I don't think twice about ordering up
two different types of parts, or even the antique light bulbs.
That entices me to forget that not everyone is so blessed.
On the other hand, somebody needs to do it, if only to
provide vicarious entertainment. A little adventure won't
hurt you at 5% of the price of audiophile interconnects.
...only a few watts, and the
distortion figures are not better than an ordinary 300B
SET and the damping factor is about 1 vs 16 ohms.
With a sensitive fullrange speaker, that's just what we need!
I put 300 watt incandescent bulbs in Google and got quite a few hits for around 5 dollars U.S each. I do not think they really care where they ship them too.
The bulbs in the in the BAF pictures look about 300 watts or they are huge 150's. It seems DIY Audio makes lots of heat.
If anyone is having problems sourcing this part I will gladly buy a few dozen and distribute them. The ceramic bases are extremely common. Hundreds of old apartment buildings here have these bulbs hanging from the ceiling on all of the hallways. Green earth is just starting to catch on in the U.S.
Nelson, any idea when the article will be published for this amp?
Tad
The bulbs in the in the BAF pictures look about 300 watts or they are huge 150's. It seems DIY Audio makes lots of heat.
If anyone is having problems sourcing this part I will gladly buy a few dozen and distribute them. The ceramic bases are extremely common. Hundreds of old apartment buildings here have these bulbs hanging from the ceiling on all of the hallways. Green earth is just starting to catch on in the U.S.
Nelson, any idea when the article will be published for this amp?
Tad
......
Actually, the faint-of-heart is the target audience, and they
will end up like you.
ya really need more than one spoiled kid , crying for adoption ?
I promise - if you (finally) adopt me , you'll see me only when you decide to visit your Ark ......
Attachments
Thanks!
If I'm able to make it to next year's Burning Amp, I know just the t-shirt I'm going to wear.
An externally hosted image should be here but it was not working when we last tested it.
se