GRollins said:
They are the same hole spacing. What makes you think you are a target?
http://www.foxnews.com/wires/2007Aug29/0,4670,InvisibleWeapon,00.html
Ah, much better. Thank you. A typo is something I can understand. I had understood John to mean something like a TO-220-ish device for the VAS, not a TO-3 for the output. In any event, those parts seem to be gone, too.
My main frustration at the moment is decent (and available to someone in the hinterlands, meaning me) TO-220 MOSFETs for the VAS. Like Goldilocks & the Three Bears, everything is either too big or too small. I can find smallish devices that can't dissipate enough heat for the Iq I want or I can find larger devices that have more capacitance than I want to tangle with, but complementary 1 to 2A MOSFETs in a TO-220 case are not just falling out of the trees.
I was briefly tempted by some of the Zetex MOSFETs, with an eye towards using two or three in parallel to help keep the heat down, but the N and P-ch parts have wildly differing capacitances and I'm unwilling to accept unequal performance from the upper and lower halves of the circuit. Just me being silly again, I guess.
As for the whole lateral vs. vertical thing, I'm neutral. Clearly there are advantages and disadvantages to each. I default to vertical MOSFETs because they are what I can get my hands on. I'm open to the idea of using lateral VAS and/or outputs, but then the availability problem rears its ugly head.
Grey
My main frustration at the moment is decent (and available to someone in the hinterlands, meaning me) TO-220 MOSFETs for the VAS. Like Goldilocks & the Three Bears, everything is either too big or too small. I can find smallish devices that can't dissipate enough heat for the Iq I want or I can find larger devices that have more capacitance than I want to tangle with, but complementary 1 to 2A MOSFETs in a TO-220 case are not just falling out of the trees.
I was briefly tempted by some of the Zetex MOSFETs, with an eye towards using two or three in parallel to help keep the heat down, but the N and P-ch parts have wildly differing capacitances and I'm unwilling to accept unequal performance from the upper and lower halves of the circuit. Just me being silly again, I guess.
As for the whole lateral vs. vertical thing, I'm neutral. Clearly there are advantages and disadvantages to each. I default to vertical MOSFETs because they are what I can get my hands on. I'm open to the idea of using lateral VAS and/or outputs, but then the availability problem rears its ugly head.
Grey
john curl said:
John,
We're on the same page regarding output Iq..."If some is good, then more is better, and too much is just enough!" My intent is class A, and class A I shall have. That's why I was threatening to hook this circuit into my water-cooled system. I can dissipate enormous amounts of heat very easily.
Grey
Mike,
I believe I recognize that circuit. Mine is different, in that I'm using complementary JFET differentials, cascoded with JFETs, into folded cascodes (sometimes JFETs, sometimes MOSFETs), themselves cascoded with MOSFETs. I'm also--at least for the time being--using John's back-to-back Vbe multiplier for bias, although I will be experimenting with other things when I (hopefully) get to the bridged version.
Oh man...and using the IRFD parts as inputs? Wow, pinout nightmare, trying to set up a board to accept those as well as everything else.
Grey
I believe I recognize that circuit. Mine is different, in that I'm using complementary JFET differentials, cascoded with JFETs, into folded cascodes (sometimes JFETs, sometimes MOSFETs), themselves cascoded with MOSFETs. I'm also--at least for the time being--using John's back-to-back Vbe multiplier for bias, although I will be experimenting with other things when I (hopefully) get to the bridged version.
Oh man...and using the IRFD parts as inputs? Wow, pinout nightmare, trying to set up a board to accept those as well as everything else.
Grey
if we're talking about mosfets suitable for use as drivers, I think (??) the Toshiba 2sk2013 and 2SJ313 pair are still manufactured. I've only seen them in a few products (some big Sony high-end amps 
) but never used them or tried to buy any myself. being Toshiba parts, they might be hard to get, too i don't really see them mentioned around here much at all.
anybody used or know anything about these? those pesky 2SK216 and 2SJ79 devices are tough to find and expensive.
mlloyd1
) but never used them or tried to buy any myself. being Toshiba parts, they might be hard to get, too i don't really see them mentioned around here much at all.anybody used or know anything about these? those pesky 2SK216 and 2SJ79 devices are tough to find and expensive.
mlloyd1
john curl said:
Hi John,
I did look at the schematic, and it still looks like driving the MOSFETs directly with that VAS is inviting lots of distortion due to the capacitance nonlinearity at the input of the MOSFETs. Tell me where I am wrong and two things will happen:
1) I will eat crow
2) the other people reading this will learn something.
Thanks,
Bob
