On Sun, 24 Jun 2018 00:59:15 -0700 (PDT), pcdhobbs@gmail.com wrote:>>It's also faster (near zero t_rr), because it's never saturated. > >Falls apart at low current though, on account of beta rolling off. The 'diode-connected transistor' is the world's simplest feedback amp. I've seen them oscillate, too--that was a weird one to debug. > >Cheers > >Phil HobbsI'll never get any sleep if you keep inventing horrors like that. -- John Larkin Highland Technology, Inc lunatic fringe electronics
JFET used as a diode
Started by ●June 22, 2018
Reply by ●June 24, 20182018-06-24
Reply by ●June 24, 20182018-06-24
On Friday, June 22, 2018 at 5:02:20 PM UTC+10, Piotr Wyderski wrote:> I need a low current, low voltage and extremely low leakage diode. > The gate junction of MMBFJ202 seems extremely well-suited for the job. > The datasheet says its absolute maximum gate current is 50mA. > Can I operate it reliably at 20mA for years? I mean, would there > be any relevant degradation mechanism or is this junction an ordinary > diode and I shouldn't worry about it?The Siliconix PAD1 asnd JPAD10 were exactly that. They were part of range that also offered higher reverse currents at lower prices. Calogic now seems to make them http://calogic.net/j_diode.html -- Bill Sloman, Sydney
Reply by ●June 24, 20182018-06-24
On 06/24/18 10:17, John Larkin wrote:> On Sun, 24 Jun 2018 00:59:15 -0700 (PDT), pcdhobbs@gmail.com wrote: > >>> It's also faster (near zero t_rr), because it's never saturated. >> >> Falls apart at low current though, on account of beta rolling off. The 'diode-connected transistor' is the world's simplest feedback amp. I've seen them oscillate, too--that was a weird one to debug. >> >> Cheers >> >> Phil Hobbs > > I'll never get any sleep if you keep inventing horrors like that. >I did a proof of concept for a long range IR remote control for Samsung some years back--it got them a factor of three increase in range, which they were happy about. The main issue, interestingly, was avoiding the forest of optical spurs put out by electronic-ballast fluorescent lights. The biggest headache was the spectral lines from the mercury emission, which (near the ends of the tubes) have important harmonics of 40 kHz that extend out past a megahertz. So naturally I built them what was basically an AM radio, complete with a 455-kHz ceramic IF filter, and used an interference filter to select an optical band with no emission lines. The point of this story is that the low frequency bias loop used five diode-connected BFT25As in series, to give a wide operating range without adding much shot noise. It worked fine at high currents, but just crapped out below about 5 nA--the diodes stopped behaving like diodes. It turned out that the 5-GHz BFT25As were slowing down so much at those low currents that they ran out of gain at 1 MHz. I switched to using the CB junctions instead, and the circuit started working. With a sub-optimal layout, a diode-connected BFT25A can oscillate above about 100 uA I_C. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●June 25, 20182018-06-25
On Friday, June 22, 2018 at 2:48:45 PM UTC-4, Phil Hobbs wrote:> There's this one, but it's a bit blurry.> https://electrooptical.net/www/sed/Bob-Pease-on-bounding-and-clamping-techniques.pdf> Cheers> Phil HobbsHere is the original readable version: Pease Bounding and Clamping https://drive.google.com/open?id=1mn0AMW76Y4nU63hYRv9w3xCycQm6w43X Phil, I sent you a copy earlier, but you didn't respond. I assume you didn't receive it or you are too busy. There is a lot of useful information in the file that may be of interest to others, so I decided to go ahead and upload it and post the url here.
Reply by ●June 25, 20182018-06-25
Reply by ●June 25, 20182018-06-25
On Monday, June 25, 2018 at 8:21:23 AM UTC-4, pcdh...@gmail.com wrote:> I didn't receive it--thanks for persisting.> Cheers> Phil HobbsThanks for the reply. Just so you don't start worrying about other emails you may have missed, I'm pretty sure the problem is on my end. This has happened once or twice before where my email server simply refused to send emails to particular addresses. I don't know why. Steve Wilson
Reply by ●June 25, 20182018-06-25
On Sun, 24 Jun 2018 12:05:48 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 06/24/18 10:17, John Larkin wrote: >> On Sun, 24 Jun 2018 00:59:15 -0700 (PDT), pcdhobbs@gmail.com wrote: >> >>>> It's also faster (near zero t_rr), because it's never saturated. >>> >>> Falls apart at low current though, on account of beta rolling off. The 'diode-connected transistor' is the world's simplest feedback amp. I've seen them oscillate, too--that was a weird one to debug. >>> >>> Cheers >>> >>> Phil Hobbs >> >> I'll never get any sleep if you keep inventing horrors like that. >> > >I did a proof of concept for a long range IR remote control for Samsung >some years back--it got them a factor of three increase in range, which >they were happy about. The main issue, interestingly, was avoiding the >forest of optical spurs put out by electronic-ballast fluorescent >lights. The biggest headache was the spectral lines from the mercury >emission, which (near the ends of the tubes) have important harmonics of >40 kHz that extend out past a megahertz. So naturally I built them what >was basically an AM radio, complete with a 455-kHz ceramic IF filter, >and used an interference filter to select an optical band with no >emission lines. > >The point of this story is that the low frequency bias loop used five >diode-connected BFT25As in series, to give a wide operating range >without adding much shot noise. It worked fine at high currents, but >just crapped out below about 5 nA--the diodes stopped behaving like >diodes. > >It turned out that the 5-GHz BFT25As were slowing down so much at those >low currents that they ran out of gain at 1 MHz. I switched to using >the CB junctions instead, and the circuit started working. > >With a sub-optimal layout, a diode-connected BFT25A can oscillate above >about 100 uA I_C. > >Cheers > >Phil HobbsI did some work on Fourier Transform Mass Spectroscopy. The old electronics had been design by a couple of chemists, and the spectrum was dominated by junk from fluorescent lights. The 30 dB excess wideband noise floor did make that look not as bad as it really was. Sadly, Agilent acquired Varian and killed off both the NMR and FTMS operations. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●June 25, 20182018-06-25
On 06/25/18 13:03, John Larkin wrote:> On Sun, 24 Jun 2018 12:05:48 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 06/24/18 10:17, John Larkin wrote: >>> On Sun, 24 Jun 2018 00:59:15 -0700 (PDT), pcdhobbs@gmail.com wrote: >>> >>>>> It's also faster (near zero t_rr), because it's never saturated. >>>> >>>> Falls apart at low current though, on account of beta rolling off. The 'diode-connected transistor' is the world's simplest feedback amp. I've seen them oscillate, too--that was a weird one to debug. >>>> >>>> Cheers >>>> >>>> Phil Hobbs >>> >>> I'll never get any sleep if you keep inventing horrors like that. >>> >> >> I did a proof of concept for a long range IR remote control for Samsung >> some years back--it got them a factor of three increase in range, which >> they were happy about. The main issue, interestingly, was avoiding the >> forest of optical spurs put out by electronic-ballast fluorescent >> lights. The biggest headache was the spectral lines from the mercury >> emission, which (near the ends of the tubes) have important harmonics of >> 40 kHz that extend out past a megahertz. So naturally I built them what >> was basically an AM radio, complete with a 455-kHz ceramic IF filter, >> and used an interference filter to select an optical band with no >> emission lines. >> >> The point of this story is that the low frequency bias loop used five >> diode-connected BFT25As in series, to give a wide operating range >> without adding much shot noise. It worked fine at high currents, but >> just crapped out below about 5 nA--the diodes stopped behaving like >> diodes. >> >> It turned out that the 5-GHz BFT25As were slowing down so much at those >> low currents that they ran out of gain at 1 MHz. I switched to using >> the CB junctions instead, and the circuit started working. >> >> With a sub-optimal layout, a diode-connected BFT25A can oscillate above >> about 100 uA I_C. >> >> Cheers >> >> Phil Hobbs > > I did some work on Fourier Transform Mass Spectroscopy. The old > electronics had been design by a couple of chemists, and the spectrum > was dominated by junk from fluorescent lights. The 30 dB excess > wideband noise floor did make that look not as bad as it really was. > > Sadly, Agilent acquired Varian and killed off both the NMR and FTMS > operations. > >Yeah, that's why I sell a lot of photon budgets. You don't know how you're doing till you know how good it _could_ be. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●June 27, 20182018-06-27
On Tuesday, June 26, 2018 at 5:45:49 PM UTC+2, John Larkin wrote:> On Mon, 25 Jun 2018 19:10:55 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > > >On 06/25/18 13:03, John Larkin wrote: > >> On Sun, 24 Jun 2018 12:05:48 -0400, Phil Hobbs > >> <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> > >>> On 06/24/18 10:17, John Larkin wrote: > >>>> On Sun, 24 Jun 2018 00:59:15 -0700 (PDT), pcdhobbs@gmail.com wrote: > >>>> > >>>>>> It's also faster (near zero t_rr), because it's never saturated. > >>>>> > >>>>> Falls apart at low current though, on account of beta rolling off. The 'diode-connected transistor' is the world's simplest feedback amp. I've seen them oscillate, too--that was a weird one to debug. > >>>>> > >>>>> Cheers > >>>>> > >>>>> Phil Hobbs > >>>> > >>>> I'll never get any sleep if you keep inventing horrors like that. > >>>> > >>> > >>> I did a proof of concept for a long range IR remote control for Samsung > >>> some years back--it got them a factor of three increase in range, which > >>> they were happy about. The main issue, interestingly, was avoiding the > >>> forest of optical spurs put out by electronic-ballast fluorescent > >>> lights. The biggest headache was the spectral lines from the mercury > >>> emission, which (near the ends of the tubes) have important harmonics of > >>> 40 kHz that extend out past a megahertz. So naturally I built them what > >>> was basically an AM radio, complete with a 455-kHz ceramic IF filter, > >>> and used an interference filter to select an optical band with no > >>> emission lines. > >>> > >>> The point of this story is that the low frequency bias loop used five > >>> diode-connected BFT25As in series, to give a wide operating range > >>> without adding much shot noise. It worked fine at high currents, but > >>> just crapped out below about 5 nA--the diodes stopped behaving like > >>> diodes. > >>> > >>> It turned out that the 5-GHz BFT25As were slowing down so much at those > >>> low currents that they ran out of gain at 1 MHz. I switched to using > >>> the CB junctions instead, and the circuit started working. > >>> > >>> With a sub-optimal layout, a diode-connected BFT25A can oscillate above > >>> about 100 uA I_C. > >>> > >>> Cheers > >>> > >>> Phil Hobbs > >> > >> I did some work on Fourier Transform Mass Spectroscopy. The old > >> electronics had been design by a couple of chemists, and the spectrum > >> was dominated by junk from fluorescent lights. The 30 dB excess > >> wideband noise floor did make that look not as bad as it really was. > >> > >> Sadly, Agilent acquired Varian and killed off both the NMR and FTMS > >> operations. > >> > >> > >Yeah, that's why I sell a lot of photon budgets. You don't know how > >you're doing till you know how good it _could_ be. > > > >Cheers > > > >Phil Hobbs > > I had about convinced myself that we could detect a single molecule in > orbit in the machine, but then Agilent killed the whole thing. > > Once we did single molecules, that would be the end of it. No point in > getting better from there."Molecule" is rather broad concept. Being able to detect a helium molecule - actually an ionised helium molecule - is nice, but the two stage mass spectrometer that I worked on (briefly) in 1992 was supposed to detect ionised protein molecules, and their fragmentation products. Very precise molecular weights - good enough to allow you to keep track of the mass defects in the atoms in the molecule - were promised (and probably delivered). -- Bill Sloman, Sydney
