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 �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
--
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