The problem with jfets is their scarcity. Supply and demand: If they were cheap and plentiful (like mosfets), then I'd say great! As it is, I feel like the few suppliers that are out there have us over a barrel.
Perhaps someone knows where we can obtain these devices at a reasonable price?
Perhaps someone knows where we can obtain these devices at a reasonable price?
Unfortunately, there's a built-in bias amongst those from the EU in that it seems that the Toshiba JFETs are--to some extent--still available over there. There are few to none available in the US and you have no control whatsoever as to whether you'll get GR or BL. VI are Unobtanium at any price. Publishing a circuit that few can build due to lack of parts is not generally Nelson's way.
Yes, the LSK389 is available, and I have some on hand, but distribution is limited. I have offered a number of times to spearhead a buy on them, but have received only a smattering of replies. I conclude that we lack critical mass on that part, at least for the time being.
I assume that we will eventually get sufficient interest for the simple reason that Toshiba has apparently discontinued the 2SK389/2SJ109. The only parts available are the ones that were already in the distribution pipeline. Once they're gone--and once the idea finally soaks in that they're gone forever--I imagine people will make more noise.
I have also experimented with the J310, and find it very useful. It's "complement" (not officially listed as such), the J271, is not available at retail, at least in the Vishay/Siliconix version. Fairchild makes both parts, but lists them as switches, not amplifiers. So far, I've limited myself to trying to locate the Vishay J271. No luck. I have contacted Vishay, but am not getting very good response from them. The way things stand at the moment, it looks as though I'd have to order 2000 units. That's more than I can use by myself, and I'd be reluctant to call it a buy since no one but me has any interest in the part.
The JFET wars continue.
Grey
Yes, the LSK389 is available, and I have some on hand, but distribution is limited. I have offered a number of times to spearhead a buy on them, but have received only a smattering of replies. I conclude that we lack critical mass on that part, at least for the time being.
I assume that we will eventually get sufficient interest for the simple reason that Toshiba has apparently discontinued the 2SK389/2SJ109. The only parts available are the ones that were already in the distribution pipeline. Once they're gone--and once the idea finally soaks in that they're gone forever--I imagine people will make more noise.
I have also experimented with the J310, and find it very useful. It's "complement" (not officially listed as such), the J271, is not available at retail, at least in the Vishay/Siliconix version. Fairchild makes both parts, but lists them as switches, not amplifiers. So far, I've limited myself to trying to locate the Vishay J271. No luck. I have contacted Vishay, but am not getting very good response from them. The way things stand at the moment, it looks as though I'd have to order 2000 units. That's more than I can use by myself, and I'd be reluctant to call it a buy since no one but me has any interest in the part.
The JFET wars continue.
Grey
Vishay/Siliconix lists the J310's transconductance as 8mS, minimum.
Linear Systems lists the LSK389's transconductance as 8mS, minimum, 20mS, typical.
The Vishay J310 isn't very expensive--$0.29 ea. at 1000 qty from Mouser. (Note that the availability problem isn't the J310, it's the J271.)
I will not initiate contact with Linear Systems about a quote unless I will be following through immediately with a purchase. No way...uh unh! I had the very devil of a time getting Lovoltech to take me seriously after they'd been hammered by 500 DIYers whining about price quotes on ones and tens of devices. They were heartily sick of hearing from DIY people and I can't say that I blame them. The lesson being that if I start negotiations with Linear Systems, I want as close to a clean slate as I can get. Good will is easily damaged.
The Vishay J310 is kinda like a 2SK170 VI on steroids. Idss starts at 24mA, minimum. Maximum is technically 60mA, but I have yet to test a part that's over 50mA. Most are in the 30-45mA bracket. Power dissipation is limited (it's a TO-92 case), so I almost always cascode in order to take advantage of the available current. Something in a TO-220 case is about right for the cascode device. Low capacitance, so it's easy to drive and wide bandwidth--thus much to my liking. Remember, I'm the guy who thinks decent bandwidth starts ca. 250kHz and prefers 3-400kHz.
(Makes Nelson nervous when I talk like that, because he'd have customers calling him from New York complaining about picking up radio stations on their gear. He generally seems to market product around 100kHz. [No, I don't blame him. I do wide bandwidth because I can get away with it out here in the wilderness.])
If I can get this pesky J271 availability problem solved, I'm likely to kiss the whole Japanese JFET industry good-bye. I'm weary of trying to find Japanese parts. I just flat-slap don't have the time (or money) to go chasing will-o-the-wisps for one squintillionth of a dB lower noise. Screw it. I'll take the higher noise. Gimme parts I can work with, not illusions and pipedreams.
Reality, man...that's the ticket.
Grey
Linear Systems lists the LSK389's transconductance as 8mS, minimum, 20mS, typical.
The Vishay J310 isn't very expensive--$0.29 ea. at 1000 qty from Mouser. (Note that the availability problem isn't the J310, it's the J271.)
I will not initiate contact with Linear Systems about a quote unless I will be following through immediately with a purchase. No way...uh unh! I had the very devil of a time getting Lovoltech to take me seriously after they'd been hammered by 500 DIYers whining about price quotes on ones and tens of devices. They were heartily sick of hearing from DIY people and I can't say that I blame them. The lesson being that if I start negotiations with Linear Systems, I want as close to a clean slate as I can get. Good will is easily damaged.
The Vishay J310 is kinda like a 2SK170 VI on steroids. Idss starts at 24mA, minimum. Maximum is technically 60mA, but I have yet to test a part that's over 50mA. Most are in the 30-45mA bracket. Power dissipation is limited (it's a TO-92 case), so I almost always cascode in order to take advantage of the available current. Something in a TO-220 case is about right for the cascode device. Low capacitance, so it's easy to drive and wide bandwidth--thus much to my liking. Remember, I'm the guy who thinks decent bandwidth starts ca. 250kHz and prefers 3-400kHz.
(Makes Nelson nervous when I talk like that, because he'd have customers calling him from New York complaining about picking up radio stations on their gear. He generally seems to market product around 100kHz. [No, I don't blame him. I do wide bandwidth because I can get away with it out here in the wilderness.])
If I can get this pesky J271 availability problem solved, I'm likely to kiss the whole Japanese JFET industry good-bye. I'm weary of trying to find Japanese parts. I just flat-slap don't have the time (or money) to go chasing will-o-the-wisps for one squintillionth of a dB lower noise. Screw it. I'll take the higher noise. Gimme parts I can work with, not illusions and pipedreams.
Reality, man...that's the ticket.
Grey