Cascode substitutions

I like those distinctions - you draw them well...

but they don't pertain to my criticism of Phil's assumptions about bitrex over-achieving on the moral principles Phil ascribes to him.

Well, if that's how it is in your circle, I'm sorry--it must be a very dog- eat dog sort of place.

But who could, for instance, freely confess to a capital crime, or lay down their life for someone else, if all their motivations were selfish? It's f ar from unknown, you know.

Cheers

Phil Hobbs

But you see it's not, not at all. It's just like everywhere else, including where religion holds sway... because it's also made of people.

Society has expectations, and life is inconvenient for those who don't measure up. That's all. No imagined higher power can improve on that, nor does (in fact it just creates a deep division in the mind that too often leads to perversion - which is all-too-apparent).

It's all self-expectations. We're social creatures, so we try to live up to social expectations... sometimes even where that might mean our own death. We've been social creatures for millions of years, but rational creatures only for a few tens of thousands - the social factors almost always outweigh the rational ones. Absolutist behavior does not, in fact, require actual moral absolutes and all the mystical nonsense those entail, only imagined ones.

There's a book I like about what humans are "naturally" like when freed from societal pressure.

It's called "Lord of the Flies"

These are questions that I struggle with every day.

If I get accurate loss numbers, I can predict performance. Sometimes you have to tell the sales guy where the limits and tradeoffs are before people sign contracts.

Prototypes take time and can't be shipped. The idea is to prototype on the computer, generate BOMs and assembly drawings, order parts, kit, build, tune, test and ship (~16 weeks release to finish). Any mechanical iterations (longer lines for instance) can add a week or more. If 50% of the orders are for custom or S/N 001 widgets, you don't want to add 50 weeks to your production load if you can avoid it.

These things are complicated enough that an EM package can't reasonably handle it all in one chunk. We do model things like couplers and the coil module but those get turned into a component model subcircuit and go into a library. As we gain bench experience, library models are refined accordingly.

If I can get within 3% on a simulation, it's a near guarantee that the production kit will yield a deliverable in a week.

Yeah, like I said -- Z and C trade off for GBW. It's "more or less" because not all devices are pure C. There's often a diffusion (distributed RC) aspect present (like a MOS gate), or complexities from incidental matching (or mismatching) due to lead/electrode geometry (stray L/C, transmission line effects).

Yup.

Of course, internal tuning means two things:

- It's made for convenience

- It's so fast that you can't practically tune it on a PCB anyway, so they have to do it for you

I've got to imagine those 60GHz transistors are darn tricky to get to behave, unless their properties are such that they're a natural fit for a planar circuit and tend to match nicely to, well, even just package and PCB pad impedances, really!

Of course, a dash of base/gate resistance goes a long way, as pretty much everyone is fond of doing. :)

Yes, for a couple reasons:

- Tuned circuits are at HF, well away from flicker noise (usually)

- Simply bandwidth reduction: less bandwidth is less noise volts or amps (but same nV/rtHz)

- In comparison with wideband circuits that might be unmatched (that is, not in a meaningful RF sense), they'll likely be designed much closer to a noise or power match, or something around there.

The goal of low noise wideband (in the sense of, freeform, transistor to transistor, wide impedance circuits) still includes matching, the algebra of matching up noise voltages/currents/resistances, and also of taking advantage of correlations if possible. (Not having much experience with low noise circuits, I don't fully understand/internalize all that's going on in Phil Hobbs' circuits, but they're excellent examples.)

Lazy, in a relative sense. Something about the differences between GaAsFETs, GaNFETs, HBTs and such; some years ago, you measured a bunch and found some gave relatively poor pulse outputs despite their bandwidth (fT?) specs.

Was that one of those parts where you saw unspecified "DC" in the datasheet, and it turned out their "DC" was 100MHz? ;-)

Distributed amplifiers are interesting tech, and there's no shortage of freely available articles and patents on them. If it works at 20GHz, it'll work at 20MHz too. Just adjust the impedances for your devices, and transmission line delays (or equivalent L/C) for the bandwidth.

I've learned one thing, though: adjusting a 9th+ order, all-pole filter, with 16 adjustable controls, is nothing any tech should have to be subjected to. My pity goes out to the first generation Tektronix people...

Yes, but impractical for lab applications, say a continuous sweep from

Tim

I tried some 45 GHz SiGe bipolars as pulse amplifiers and was disappointed with the speed. Maybe I did something wrong; Joerg seems to have had better results.

Phemts seem to have no Ft equivalent. They seem to act like an infinitely fast gadget with parasitic capacitance and lead inductance. They switch *fast*

The Avago enhancement phemts can be handy.

That was a Hittite absorptive analog mux. It's supposed to terminate unselected input ports, and does above 100 MHz. The data sheet says "DC TO 4 GHz" in huge type.

Look for a Tek 545 schematic!

Heck, it had almost nothing; the 517 was king:

The 585 peaked at 100MHz of mostly-hollow-state bandwidth, but by then they introduced distributed deflection CRTs, which did a much nicer job. Only needing tens of volts, they used five 6DJ8s (dual triodes, comparable to a BF862 with 1/3 the transconductance, lower Ciss, comparable Coss, 10 times the operating voltage... and who knows how much more noise :) ) to drive a somewhat beefy pentode to finally drive the deflection plates.

Industrial art. A shame they aren't useful anymore, but at least a few people appreciate them for what they are.

Tim

But the 547 was beautiful, the last of the big ole Tek plugin scopes. The CRT electron optics was amazing. I have a few.

Here's the 547 CRT:

The 519 was a 1 GHz scope. They avoided the bandwidth limits of a vertical amplifier by not having one.

Evolution. Monkeys get upset when they are treated unfairly. Social animals need rules and mechanisms that stop free-loaders from exploiting everybody else.

But the survival statistics do. For a lot of situations, you (and your off- spring) will only do well if the tribe cooperates for the good of all.

It's mostly around the edges. Civilisation is all about expanding the group of people we treat as if they were members of our tribe - which should be everybody, these days, except possibly active members of ISIS and Donald Tr ump supporters.

It wouldn't last long - though running away in battle does have it's up sid e, in that "he who fights and runs away, lives to fight another day".

Double-crossing all your friends isn't a way to sustain good social relatio nships, but if you are very good at moving to new places and making new fri ends it could work, but not very often, granting that six degrees of separa tion means that word travel fast.

This is not the way RF amplifiers are usually built. More common is to split the input with a 180-degree hybrid, amplify each half with an NPN transistor, and then recombine the outputs with another 180-degree hybrid. No PNPs needed. Bandwidth can be of the order of three decades.

Jeroen Belleman

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stors for

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It's been around for a while. It caught my attention around 1990, and I wou ld have liked to design it into our 0.5nsec +7/-7V beam blanker (to drive t he RF NPN's that formed the output) but what we had was fast enough at the time.

We couldn't get anything to behave sensibly without "base-stoppers" - 20R t o 30R of surface mount resistor in series with the base, and close to it.

The right value of ferrite bead would presumably have been better (and we k new it at the time), but back then there weren't all that many ferrite bead s around and they weren't all that well characterised.

Don't know. The beam blanker that worked used BFT93 PNP drivers, to drove N PN HP RF power transistors at the output, and the BFG31's would have replac ed them, if they'd worked. The whole circuit was about charging and dischar ging Miller capacitance fast, rather than linear amplification as such, tho ugh it looked linear enough and we had a low current mode for moving the el ectron beam around a bit without actually turning it fully off.

Since monkeys and apes have ideas about fairness, it's very likely that at least some of what we have is a universal innate quality of humans.

It actually about school-boys, and it's a fable, not a documentary.

Count the number of dissatisfied customers, and figure it as a proportion of the number of people interacting with the saint/humanitarian/mafia-don/drug-dealer.

The drug-dealer may come out looking relatively good - if the drugs being dealt are pure.

Not hard enough, by the sound of it.

Shooting up in a back alley isn't a good way of being a heroin addict. Medi cal professionals who can get pure heroin and clean needles can sustain a h abit for years, then kick it when they grow out of it without showing any v isible signs of damage.

Making heroin addiction a dangerous vice may not be the best way to cope wi th it. The Dutch go in for "harm reduction" - once you are registered as an addict you can get get your fix on a regular basis. You have to take it un der supervision, so you can't sell it to somebody else. It seems to work, a nd makes drug-dealing less profitable for the dealers.

The US ran it's "Great Experiment" with prohibiting ethanol, and worked out that it didn't work. Sadly, they don't seem to have noticed that the resul t generalises to other recreational drugs.

That's an odd claim. The distributed amplifier was invented rather before ICs - in 1936. Bill Percival was still working at EMI Central Research when I met him there in 1978.

The Wikipedia description does lay some emphasis on the transmission line nature of the beast, and inductors don't integrate all that well.

A hybrid on a a ferrite substrate might work better, and it's interesting to speculate about what one might be able to do with high-temperature super-conductors.

Well yeah, but I was hoping to get away from that. That's why we invented complementary transistors, isn't it? ;-)

And as I mentioned elsewhere, I'm open to using conventional (non-complementary) push-pull, so yes, with hybrids. But if we've got PNPs that are suitable, why not use them? (But also as I mentioned, I might not be able to, anyway, for junkbox selection / suitability / power anyway.)

Tim

Mmmm, not too much special I would think. I don't know of many superconductor applications that don't depend on quantum behavior (e.g., SQUIDs), except for some RF resonator applications. But I haven't read much about it, and there are definitely some interesting things that could be done.

I think those are mostly or all type 1 though: type 2 superconductors are rather lossy, and might not be suitable for RF. (Q factor of type 1 superconductors is still poorly understood, from what I've heard, but can still result in Q factors in the 10^7 range -- better than quartz crystals, and at much higher frequencies. And, I suppose you don't have to worry about tempco, because the boiling helium takes care of that for you!)

Tim

High temperature superconductors work at liquid nitrogen (though not with high magnetic fields) and some microwave guys were reputed to be using them to get high Q inductors. I think Jan Panteltje was playing around, which isn't exactly mnainstream ...

Chimpanzees do seem to have some conceptions of fairness, as in if they see the other ape taking food from their tray unfairly when they're not getting any (in an experiment designed to test this) they'll flip the tray and trash it.

But monkeys and apes live in societies. Not terribly sophisticated ones, but societies nonetheless. Some of them even make tools!

And IIRC chimps are pretty poor at cooperation. If there's a heavy rock on a bucket of food just large enough that only two apes can move it they'll go and try to get a human to move it if there's one around, but if it's just two apes they'll sit around all day scratching their heads not knowing what to do.

If people didn't often use art to get at essential "truths", most art would be pretty bad.

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