Brad
IMHO no need for that. One of the good things by a discrete design is that the users have access to all the nodes, and can design their own prefered compensation.
BTW: Billy Budd
Did I miss some interesting posts?
Cheers
Stein
And there's that prevalent anti-bipolar bias. I was cheered to see that Jim Boyk (with Gerald Sussman, who undoubtedly did most of the math-and-modeling heavy lifting in the article) finally had some good things to say about them in a paper about IM distortion and feedback. Remember that this is the guy who had T shirts made that said "Digital finishes what the transistor began", and in his class at Caltech had students build simple transistor and tube gain stages and judge which one sounded better.
[EDIT] And Boyk and Sussman point out that matched JFETs as, in their example, a push-pull complementary output stage, have distortionless performance. They do acknowledge that their FET models are as ideal square-law devices, with a host of other real attributes ignored. The contact, or as PRR might call it, "dead" resistance, that's not involved in the transistor action, is enough to spoil this "perfection".
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It's safely in secured subterranean storage for some time now, along with a few other treasures, although my collection is doubtless dwarfed by those of some of the other patrons with much higher incomes.
SY knows where it is, more-or-less, but he's not too close and doesn't have a key
You're out of context here a little, their example was MOSFET's in extreme class A, gates actually pushed outside the rails by ideal sources, Vgatedrive >> VT at all outputs. JFET's can't do that.
Some other comments about distortion and degeneration made in the last few posts don't take into account input voltage compliance. Boyk and Sussman use .005V for bi-polar vs .150V for JFETs to put them on equal ground for distortion. This difference is the whole basis of JFET vs bi-polar performance with respect to slew rate vs gm and BW.
1948 Graham's Port is my last precious bottle.
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Thanks Scott. I didn't have the paper handy and had forgotten they were using DMOS.
To go with the Petrus if it is ever drunk, I've a second bottle of one drunk years ago, a 1959 Yquem. When I drank the first Yquem, circa 1982, it was preceded by the top wine of my experience to date, a 1945 La Tache, which had no right to be in such good shape. I later noticed that Broadbent accorded both the La Tache and the d'Yquem six stars (five being his conventional maximum).
Three of us drank the La Tache and half of the Yquem, which I siphoned the other half of into a half-bottle for future consumption. Well, that resolve lasted about two more days.
I am wondering whether to keep and someday use the rare jFETs or just throw them away -- I have a stash of 2SK389, K146, K147, J72, J73, J109 and a whole bunch of 170/74 all grouped by Idss. And, some other types which are great but obsolete now. Cant give them to the undeserving family members. I know what they would do with them. What would you do with them?
I give my extra stuff to MIT (Jerry Sussman actually) I doubt much gets used by students anymore. In another decade or so who knows.
Well there is a market on eBay for such. Curl mentioned SK389s going for about ten bucks a pop "in quantity". Which reminds me, I need to send off a couple pairs of roughly-matched 2SK389V and 2SJ109V. Been getting busier lately, finally! And it's hot outside, even if a "dry heat".
Keep what you have Richard. They are too good for current sources, AND they have too much Gm and too low Rd to be good current sources anyway. I am sure that you will find many needy people here who will be glad to take a set of devices, or more at a good price. You might as well make it worth your while for the 'hassle factor' but you could easily make some 'new friends' by doing so.
Three of them in fact. Two-buck Chuck (Charles Shaw, from Trader Joe's) fools many tasters, although bottle variation is substantial, since they buy grapes from all around. I still have one browning bottle of the 2000 Chardonnay saved for friend Kathy, who bought cases of it and never tasted it. I started giving it away and drinking it up sometimes, and she said Well I at least want to taste it! Are you sure? The bottle has some particulate matter floating in it now, no idea what it is
The stories circulating when the stuff first hit were hilarious. Although none of us had ever heard of the allegedly venerable C Shaw of Napa, CA, one account was that after 9-11, airplanes had to stop carrying bottles with cork seals, as they didn't want to risk having a lethal corkscrew on board. All complete rubbish. The other promulgated falsehood was that it was a short-term deal. I saw people carting out enough wine to bathe in, and had another guy ask if storing it upright would be o.k. for a while. Well, since the particle-board-like corks never get any wetting action to speak of anyway, yes, that will be fine to do.
In 1999 I used to consume nice South Aftican wine, about 60 Rands per bottle. Exchange rate was about 8:1, so it would mean about $7-$8 per bottle. But later I discovered that 10 times cheaper (less than $1) Chateau Libertas vine was great as well! SA's Oupa of red wines, Chateau Libertas, now 80 | wine.co.za
+1 on what John said - keep them, they're too valuable.
(I've been buying complete broken Japanese integrateds, knowing that they had 2SK146's in their phono stages only to get a couple for my own needs. No such luck with 2SJ72/73's though...)
Other parts I'd love to see more available are the ultra-low base spreading resistance ones like the Toshiba 2SA1316 and 2SC3329. Zetex claims that they have some comparable parts, which I have yet to try.
I spotted some 1316 in the phono input stage of a mid-level NAD standalone preamp. Decent for MC, and I suspect the switching between MC and MM in part changed the bias current for the devices. Suffice it to say, with an open input MC is VERY noisy.
If you wouldn't heed John Curl good advise, I'd built a preamp, including phono stage and line stage with few pairs of matched IDSS 2SK389/2SJ109.
Save rare jFETs for repairs -
I guess I'll just hold them for repair work if I get my hands on something good that needs repair.
Meanwhile, for historical purposes (or hysterical) the all bipolar version of the topology I did 30 years ago is attached. I would only add a dc servo and put the output 6.8v zener to the output emitter (causes Ic to increase to 17mA - so TO5 or greater pwr needed). Or add the output stage I used with jFET input version shown earlier for driving low Z loads. The complimentary push-pull topology has turned out to be very popular and versatile. -Dick Marsh
I guess I'll just hold them for repair work if I get my hands on something good that needs repair.
Meanwhile, for historical purposes (or hysterical) the all bipolar version of the topology I did 30 years ago is attached. I would only add a dc servo and put the output 6.8v zener to the output emitter (causes Ic to increase to 17mA - so TO5 or greater pwr needed). Or add the output stage I used with jFET input version shown earlier for driving low Z loads. The complimentary push-pull topology has turned out to be very popular and versatile. -Dick Marsh
Attachments
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