Ahh... i always kind of assumed that you were the Tomo from "Tomo's CCS" and (now that ive had proper looks at it) the headwize article.
Thank you a lot for the explanations on MOSFETs, in all honesty i did not have much idea at all on how they work or exactly what they are.
Thanks for noticing i had hooked up the LM317 CCS wrong, if you notice in the first schematic it was correct, but for some reason i managed to screw it up in the second one. All fixed now though
(From what i have read most people tend to swing towards the resistor instead of the CCS, but i am kind of curious to hear both)
I am very confused though, and i think that what you are saying contradicts what i understand from others (Oh the wonderfull world of audio
)
About "pulling" (or what ever the correct word is) opamps into class a, the idea of it is to keep the output stage turned on the entire time in order to increase linearity. (And also activate on the PNP/NPN, i forget which). To do this you work out the amount of current the opamp will be dilivering and then add a current source that draws greater than that amount.
I figured the best way to work that out would be to use the impedance of the MOSTFET (as the opamp saw it) to work out the max current draw and then choose a nice CCS to draw current from the opamp. But according to what you are saying - there is no way to do that?
In the headwize addendum (on the schematic i posted above my second schematic) the guy has added a 4.7k resistor to ground after the opamp output in order to draw the opamp into class A. I do not like the idea of a resistor as a current source (after reading tangent's article on biasing opamps into class A) and was wondering which Current Regulating Diode to replace it with.
But according to what you are saying - there is basically no way to do this?
Also, you say:
Quote:
Originally Posted by Tomo
but that would mean your MOSFET gate have relative direct path B+ (V+). Gate is very sensitive. You can destroy it with a small spark, let alone brief moment of high voltage.
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The MOSFET gate would only have a relative direct path to GND, not to the +15v. All i would be doing is replacing the 4.7k resistor with a CCS instead.
Rob.