Reply by February 27, 20182018-02-27
On Tuesday, August 14, 2012 at 1:11:09 PM UTC+10, John Larkin wrote:
> OK, I need to charge a capacitor with a stable constant current. The > desired slope is about a volt per nanosecond. > > So I did this: > > https://dl.dropbox.com/u/53724080/Circuits/Fast_Ramp.JPG
That link didn't work for me.
> Things like this tend to oscillate, so I used a fairly slow, high-beta > transistor, BCX71K. The ferrite in the collector is supposed to > isolate the ramp cap from the transistor capacitance and make the ramp > linear. > > Well, the ramp looked not much better than an R-C curve, and the BCX71 > oscillates at 80 MHz. Increasing R1 from 50 to 150 ohms kills the > oscillation and makes the curvature worse. > > So we went to the opposite extreme, a BFT92, a 5 GHz PNP. Typ beta is > 50! The ramp is now visually linear, and the oscillation frequency > went up some. Tried a ferrite instead of R1, and it *really* > oscillates. A 100 ohm base resistor seems to work.
Those 5GHz wide-band transistors do seem to need a base-stopper.Back in 1989, when we were making this kind of fast ramp, something between 22R and 33R was usually enough - we were using strictly L-trimmed surface mount resistors, which tend to have rather low parallel capacitance, and we put them pretty close to the base connection. I had the idea that getting the base impedance right some other way might stop them oscillating, but never got anywhere with testing the idea - other problems kept on getting in the way. -- Bill Sloman, Sydney
Reply by February 27, 20182018-02-27
Ur mum gay lol
Reply by josephkk August 21, 20122012-08-21
On Sun, 19 Aug 2012 12:49:57 -0500, legg <legg@nospam.magma.ca> wrote:

>On Fri, 17 Aug 2012 22:03:24 -0700, John Larkin ><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: > >>On Fri, 17 Aug 2012 19:38:35 -0700, josephkk >><joseph_barrett@sbcglobal.net> wrote: >> > >>I hate to brag about how old I am, but Spice was introduced to the >>world in 1973 >> >>http://en.wikipedia.org/wiki/SPICE#Origins >> > >Funny. Any idea where ECAP, PCAP and Sceptre fit in? Not a mention in >the 'pedia. Little better on the web. > >RL=20
Sceptre was somewhat similar to spice but oriented about transient radiation effects. My dad was using that while i was a teen also. Plus = i must mention that Wikipedia is not always right. If you look it up spice 2 was released in 1972, spice 1 previously known as CANCER was much earlier (mid 1960s). ?-)
Reply by Michael A. Terrell August 20, 20122012-08-20
Jamie wrote:
> > The only Phd I brag about is the one in my tool shed.
So, the 'post hole digger' owns a 'Post Hole Digger'.
Reply by August 19, 20122012-08-19
On Monday, August 13, 2012 11:11:09 PM UTC-4, John Larkin wrote:
> OK, I need to charge a capacitor with a stable constant current. The > > desired slope is about a volt per nanosecond. > > > > So I did this: > > > > https://dl.dropbox.com/u/53724080/Circuits/Fast_Ramp.JPG > > > > Things like this tend to oscillate, so I used a fairly slow, high-beta > > transistor, BCX71K. The ferrite in the collector is supposed to > > isolate the ramp cap from the transistor capacitance and make the ramp > > linear. > > > > Well, the ramp looked not much better than an R-C curve, and the BCX71 > > oscillates at 80 MHz. Increasing R1 from 50 to 150 ohms kills the > > oscillation and makes the curvature worse. > > > > So we went to the opposite extreme, a BFT92, a 5 GHz PNP. Typ beta is > > 50! The ramp is now visually linear, and the oscillation frequency > > went up some. Tried a ferrite instead of R1, and it *really* > > oscillates. A 100 ohm base resistor seems to work. > > > > > > -- > > > > John Larkin Highland Technology Inc > > www.highlandtechnology.com jlarkin at highlandtechnology dot com > > > > Precision electronic instrumentation > > Picosecond-resolution Digital Delay and Pulse generators > > Custom timing and laser controllers > > Photonics and fiberoptic TTL data links > > VME analog, thermocouple, LVDT, synchro, tachometer > > Multichannel arbitrary waveform generators
What the heck is wrong with a NIC??? Your slew rate is well within the reach of modern high speed amps: Please view in a fixed-width font such as Courier. . . . . .------[R]--+-------[R]---. . | | | . --- | |\ | . /// '--|-\ | . | \ | . | >------+---> . | / | . .--|+/ | . | |/ | . | | . | | . Vref>----[R]--+-------[R]---' . | . ------+ . | | . |- === . sw>--| | . |--------+ . --- . /// . . .
Reply by krw...@att.bizzzzzzzzzzzz August 19, 20122012-08-19
On Sun, 19 Aug 2012 09:15:29 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Sat, 18 Aug 2012 21:28:39 -0700, John Larkin ><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: > >>On Sat, 18 Aug 2012 18:17:36 -0700, Jim Thompson >><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >> >>>On Sat, 18 Aug 2012 13:24:08 -0700, John Larkin >>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>> >[snip] >> >>Of course I have IP. But I use it in my own products and don't sell it >>for a one-time consulting fee. In a few cases, I license it, which >>just means that someone else does the manufacturing to make my ongoing >>revenue stream. But they don't own it. >> >> >> I have 18 patents. How many do you have? >>> >>> ...Jim Thompson >> >> >>One, but I have rights to use it. > >Patent number?
Maybe 7,019,307?
>>How many of your 18 are assigned to >>someone else? >> > >All, but I receive royalties from five. > > ...Jim Thompson
Reply by legg August 19, 20122012-08-19
On Fri, 17 Aug 2012 22:03:24 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

>On Fri, 17 Aug 2012 19:38:35 -0700, josephkk ><joseph_barrett@sbcglobal.net> wrote: >
>I hate to brag about how old I am, but Spice was introduced to the >world in 1973 > >http://en.wikipedia.org/wiki/SPICE#Origins >
Funny. Any idea where ECAP, PCAP and Sceptre fit in? Not a mention in the 'pedia. Little better on the web. RL
Reply by Jim Thompson August 19, 20122012-08-19
On Sat, 18 Aug 2012 21:28:39 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

>On Sat, 18 Aug 2012 18:17:36 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Sat, 18 Aug 2012 13:24:08 -0700, John Larkin >><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>
[snip]
> >Of course I have IP. But I use it in my own products and don't sell it >for a one-time consulting fee. In a few cases, I license it, which >just means that someone else does the manufacturing to make my ongoing >revenue stream. But they don't own it. > > > I have 18 patents. How many do you have? >> >> ...Jim Thompson > > >One, but I have rights to use it.
Patent number?
>How many of your 18 are assigned to >someone else? >
All, but I receive royalties from five. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by Jim Thompson August 19, 20122012-08-19
On Sat, 18 Aug 2012 21:28:39 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

>On Sat, 18 Aug 2012 18:17:36 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Sat, 18 Aug 2012 13:24:08 -0700, John Larkin >><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >> >>>On Sat, 18 Aug 2012 11:01:01 -0700, Jim Thompson >>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>> >>>>On Sat, 18 Aug 2012 10:27:34 -0700, John Larkin >>>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>>> >>>>>On Sat, 18 Aug 2012 09:46:55 -0700, Jim Thompson >>>>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>>> >>>>>>On Sat, 18 Aug 2012 18:18:51 +0200, Fred Bartoli <" "> wrote: >>>>>> >>>>>>>Phil Hobbs a &#2013265929;crit : >>>>>>>> dagmargoodboat@yahoo.com wrote: >>>>>>>>> On Aug 15, 4:34 pm, Phil Hobbs >>>>>>>>> <pcdhSpamMeSensel...@electrooptical.net> wrote: >>>>>>>>> >>>>>>>>> [...] >>>>>>>>> >>>>>>>>>> The NPN/PNP series-shunt pair (the one that folks with nothing better to >>>>>>>>>> do are are slagging each other off about at the moment) runs the driver >>>>>>>>>> transistor at constant I_C, and lets you use a much faster NPN to >>>>>>>>>> stiffen the PNP at high frequency. Try simulating it--it's really good >>>>>>>>>> medicine. >>>>>>>>>> >>>>>>>>>> (I spent most of July up to my ears in high performance laser noise >>>>>>>>>> cancellers, which rely on a lot of those sorts of tricks, so I'm pretty >>>>>>>>>> well up on all this at the moment.) >>>>>>>>> I like the pseudo-Darlington, I'm just leery because I had those >>>>>>>>> scream wickedly once using fast transistors. I don't think I ever >>>>>>>>> fixed it. >>>>>>>>> >>>>>>>>> It has a bunch of advantages here, including reducing the base current >>>>>>>>> i(b) error. >>>>>>>>> >>>>>>>>> Here's a skeleton idea for a Bloggs-Hobbs hybrid: >>>>>>>>> >>>>>>>>> Vcc Vcc >>>>>>>>> -+- -+- >>>>>>>>> | | >>>>>>>>> | .-. R1 >>>>>>>>> | U1 | | 120 >>>>>>>>> | LM385 '-' >>>>>>>>> | -adj | >>>>>>>>> .---' | >>>>>>>>> A<-----R2-----+---------. >>>>>>>>> | | | >>>>>>>>> | |<' Q1 | >>>>>>>>> +-----+-----| BFT92 | >>>>>>>>> | | |\ | >>>>>>>>> R4 .-. --- C1 | |/ Q2 >>>>>>>>> 1K | | --- +--f.b.-| BFP640 >>>>>>>>> '-' | | |>. >>>>>>>>> | === .-. | >>>>>>>>> === | | R3 | >>>>>>>>> '-' 600 | >>>>>>>>> | | >>>>>>>>> '---------+----> >>>>>>>>> >>>>>>>>> R2's a pathetic provision for isolating U1 from the nS stuff. The >>>>>>>>> whole thing needs stabilizing against UHF oscillation, these are just >>>>>>>>> the bones. >>>>>>>>> >>>>>>>>> -- >>>>>>>>> Cheers, >>>>>>>>> James Arthur >>>>>>>> >>>>>>>> It wouldn't need much more than that, I don't think. Series-shunt pairs >>>>>>>> have poor stability when the transistors are about the same speed, due >>>>>>>> to having two lags in the loop, but the BFP640 is ~10x faster than the >>>>>>>> BFT92, which helps a lot. (Reducing the BFT92's collector current makes >>>>>>>> the difference wider and helps with stability.) >>>>>>>> >>>>>>>> I used the BFP640 as a cascode for an ATF38143 pHEMT in a very quiet >>>>>>>> charge-sensitive preamp (noise floor ~10 electrons per inverse >>>>>>>> bandwidth), and all it needed was an 0402 bead in the base--no worries >>>>>>>> at all. >>>>>>>> >>>>>>>> Cheers >>>>>>>> >>>>>>>> Phil Hobbs >>>>>>>> >>>>>>> >>>>>>> >>>>>>>I had a try at John's pb... >>>>>>> >>>>>>>Here it is, using a current source bootstrapped bootstrapped current >>>>>>>source (yes I really meant to say that :-). >>>>>>> >>>>>>>I use the +8V/-5V supplies that you mentioned IIRC and only 3 x BFT92. >>>>>>>Some temperature dependent biasing is also provided but I relied on the >>>>>>>8V supply stability over temp which may be wrong and you may have to >>>>>>>adapt a bit. >>>>>>> >>>>>>>Some simulations including parasitics give pretty interesting results. >>>>>>>Note that my BFT92 model VAF is 11V ! Is this low real ? (I don't have >>>>>>>any to measure it) >>>>>>> >>>>>>>Despite this this circuit shows excellent results (in simulation, so >>>>>>>apply the usual grain of salt). >>>>>>> >>>>>>>Still: >>>>>>>* better than 0.1% linearity with this low VAF figure which can be >>>>>>>further improved >>>>>>>* start up transients are under 1ns and the integrated error is >>>>>>>negligible... >>>>>>>* 0.25% dispersion at 3.9V final value over temperature (-50/+75) (I >>>>>>>relied on your 8V supply stability, so you may have to adapt a bit) >>>>>>>* low output impedance, so no need for buffering if you just drive one >>>>>>>input (modeled here as the 2pF capacitance) and can stand the temp >>>>>>>dependent offset at start (or you can still add a NPN buffer to >>>>>>>compensate for VBE) >>>>>>> >>>>>>> >>>>>>>Here's a LTspice netlist. It's just for the drawing as I don't use it >>>>>>>for sim and have almost no BJT models and even less with parasitics... >>>>>>> >>>>>>>If you want to see the results I'll make a pdf. >>>>>>> >>>>>>> >>>>>>>******************************************** >>>>>>> >>>>>>>Version 4 >>>>>>>SHEET 1 948 1004 >>>>>>[snip .ASC, retrieve at Message-ID: >>>>>><502fc06b$0$6124$426a74cc@news.free.fr>] >>>>>>>SYMATTR InstName J1 >>>>>>>SYMATTR Value NE3509 >>>>>>> >>>>>>> >>>>>>> >>>>>>>******************************************** >>>>>> >>>>>>Finally! An inductor used properly. I can envision other such >>>>>>structures that are possibly simpler, but I ain'ta-gonna give Larkin >>>>>>no free ride ;-) >>>>> >>>>>In other words, as usual, you contribute nothing on topic. All you >>>>>remember how to do is boast and cluck. >>>> >>>>Just as long as I keep you frothing at the mouth ;-) >>> >>>You delude yourself, old man. >>> >>> >>>> >>>>> >>>>>I don't think you could play the circuit design game if you wanted to. >>>>>You are hiding your senility behind "not helping Larkin." You're >>>>>useless off-chip anyhow. >>>>> >>>>>> >>>>>>Good job, Fred! >>>>>> >>>>> >>>>>So, you approve of Fred's design? >>>> >>>>I couldn't run it, but it certainly is heading in a better direction >>>>than all those insane IB correctors. >>> >>>I did Ib correction with one resistor and half of a dual opamp. >>>Microwave PNPs have insane betas, like 20. You propose to ignore base >>>current over temperature? Yeah, right, you have a better way to do >>>this, but you won't reveal it. Pitiful bluff. >> >>Crap! I have ignition systems (still) running in cars where the >>control device had a nominal beta of THREE with IB correction. Read >>Frederiksen's tome... I invented such schemes. >> >>> >>> >>>> >>>>What don't _you_ post your solution as an LTspice ASC file so that >>>>everyone can verify your brilliance ?:-) >>> >>>I wouldn't Spice my fast current source designs. The fast stuff would >>>be inaccurate because the part models aren't good enough. The slow >>>loops, like the Ib correction, are way too simple to need Spicing. >>> >>>> >>>>What have you designed lately? Yesterday I designed a magnetically >>>>controlled sign board :-) >>> >>>EUV light source controller. EUV energy/waveform digitizer. Particle >>>discriminator. Four different laser drivers. LVDT/synchro simulator. >>>USB picosecond pulse generator. Ethernet interfaced >>>picosecond-resolution 5-channel time stamper. NMR gradient driver and >>>temperature controller combo. Bunch of fiberoptic stuff. A couple of >>>fast high-voltage pulsers. >>> >>>The thing I like about designing this stuff is that I release the >>>drawings to production and they crank out copies, and revenue, for a >>>decade or so afterwards. I never sell IP or engineering. >> >>You don't have any to sell. > >Of course I have IP. But I use it in my own products and don't sell it >for a one-time consulting fee. In a few cases, I license it, which >just means that someone else does the manufacturing to make my ongoing >revenue stream. But they don't own it. > > > I have 18 patents. How many do you have? >> >> ...Jim Thompson > > >One, but I have rights to use it. How many of your 18 are assigned to >someone else? > >How much of the IP in your active patents can you sell? Patents are a >suckers's game if they are assigned to someone else. You get to brag, >but they get the money.
I get royalties for 5 of them... keeps me in wine ;-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by Phil Hobbs August 19, 20122012-08-19
dagmargoodboat@yahoo.com wrote:
> > On Aug 16, 10:01 pm, Phil Hobbs > <pcdhSpamMeSensel...@electrooptical.net> wrote: > > John Larkin wrote: > > > > > On Thu, 16 Aug 2012 17:28:16 -0400, Phil Hobbs > > > <pcdhSpamMeSensel...@electrooptical.net> wrote: > > > > > >On 08/16/2012 05:19 PM, John Larkin wrote: > > > >> On Thu, 16 Aug 2012 12:20:49 -0700 (PDT), dagmargoodb...@yahoo.com > > > >> wrote: > > > > > >>> On Aug 16, 11:29 am, Jim Thompson<To-Email-Use-The-Envelope-I...@On- > > > >>> My-Web-Site.com> wrote: > > > >>>> On Thu, 16 Aug 2012 07:39:04 -0700 (PDT), dagmargoodb...@yahoo.com > > > >>>> wrote: > > > > > >>>>> On Aug 15, 10:43 pm, John Larkin > > > >>>>> <jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > > > > > >>>>>> Hey, how about this? > > > > > >>>>>>https://dl.dropbox.com/u/53724080/Circuits/Isrc_simpler.JPG > > > > > >>>>> It's kind of a variation on Phil's active inductor. That defeats all > > > >>>>> the oscillation modes I can think of so far. (c-b, e-b, c-e)(Which > > > >>>>> means little, since circuits are so ingenious inventing new ones.) > > > > > >>>>>> Ludicrously simple. No Miller nonsense. Might not oscillate. MMBTH81 > > > >>>>>> would have about 2 pF out, or BFT92 would have about 0.75 but lower > > > >>>>>> beta. > > > > > >>>>> You could use the beta-cancellation trick. But, stray and parasitic > > > >>>>> capacitance will be big factors compared to a 10pF integration cap. > > > > > >>>>>> If this works, I should have done it years ago. > > > > > >>>> Yup. But I'd still add a base resistor, for the very reasons Gerhard > > > >>>> Hoffmann brought up... the output Z of the OpAmp is a big unknown (*). > > > > > >>>> (*) Which brings to mind... maybe add some DC load to the OpAmp to > > > >>>> keep it out of the class-B region. > > > > > >>> I agree with both those points, and meant to mention them. I don't > > > >>> trust the op-amp to behave nicely to impulses, or its output to be > > > >>> stiff. I'd expect the output to be hi-z on this timescale. > > > > > >>> If anything I'd be tempted to bypass the bjt's base to the supply > > > >>> rail. The BJT then handles the fast stuff. Isolate that capacitive > > > >>> load from the op amp's output with a series resistor, and stabilize > > > >>> the op amp loop itself with a feed-forward cap. Standard stuff. > > > > > >>> Does it all matter? Unclamping the integration cap will feed-thru a > > > >>> small impulse through to the bjt / CCS. After that, it's pretty > > > >>> clean. So, the op-amp's output impedance might not matter, but I > > > >>> suspect it will. > > > > > >>> I invented loading LM324 outputs all by myself waayyyy back as a punk > > > >>> kid, to stiffen them up and kill the crossover THD. Of course > > > >>> everyone else on the planet thought of it too. :-) > > > > > >> Me too! And I also invented loading the charge pump phase detector in > > > >> the 4046. > > > > > >> I also invented the successive-detection log video detector, and the > > > >> dual-slope ADC. I did those at times when I could have patented them. > > > >> I'd be smoking seegars on the Riviera. > > > > > >DLVAs have been around since at least the war: e.g. US Patent 2577506 to > > > >Belleville, filed 1945. > > > > > >Cheers > > > > > >Phil Hobbs > > > > > Oh well. But I did invent the dual-slope some years before Fairchild > > > (?) patented it. > > > > I used to be a big fan of the Intersil ICL7109 back in the day. Dual > > slope was magic. > > > > Cheers > > Don't forget the ICL7135 ... this datasheet was updated in 2007. > http://www.intersil.com/content/dam/Intersil/documents/fn30/fn3093.pdf > > I lusted for that part in a design ages ago, but it was much too > expensive, ~$15 IIRC (roughly $40 today). I rolled my own instead: > 82c53, 74HCxx state machine controller, etc. It was a big upgrade > over our existing products, all 12-bit. > > I got a bucket of galvanically isolated 4-1/2 digit ICL7135 isolated > LED digital panel meters at a flea market not too long ago, for less > than the 1pc chip price back in the day. > > -- > Cheers, > James Arthur
That would have been a nice part a few years back, ~15 bits for $3. DPMs are about the only reasonable use for one nowadays, of course. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net