Quotation of the day

[Homer J Simpson]

Have you looked at the Supertex depletion-mode mosfets? They look
tubish alone, and could be cascoded above a gaasfet for higher Gm and
speed.

I'll make a note and take a look.

 

[Homer J Simpson]

But who would ever be antagonistic about NZ ??? When did NZ last start a
war for
example ?

France when they sank the Rainbow Warrior.

 

[Homer J Simpson]

Of course if anyone did invade us, they would discover that kiwis have 33x
as many guns as our army (1 million c.f. 30,000), are extremely inventive,
and *really* dont like being pushed around.

And are well capable of living in the bush and picking off the odd invader
(along with the wapiti).

Maybe the Maori could take up cannibalism again - or threaten too.

 

[Homer J Simpson]

That's the spirit !

I really sometimes wonder why Australia bothers with its F111s quite
frankly. Do they
expect Indonesia to invade ? If they did would a few F111s help ?

I still don't know why Canada bought those crap submarines from the UK.

 

[Jim Thompson]

Jim Thompson wrote:

[snip]

So ask a technically useful question already ;-)

...Jim Thompson

OK,

Im playing with an el-cheapo smps controller. Its peak-current-mode
control, and uses the BE junction of an NPN to detect peak current, and
turn the switch off. Of course Vbe varies strongly with T.

Normally I use a TL431 etc for voltage feedback; it has a nice stable
reference. I just choose my current sense resistor for min Vbe (max T),
and the magic of -ve feedback makes sure all is well. yay.

the circuit is pretty simple, the 431 pulls down on a pnp (crappy
mirror) which feeds current into an R, also connected to the base (there
is an R from B to Rs) so the base voltage is the sum of IRs and the
error amp output voltage.


This time, however, I want to use it as a current regulator. There is
still a setpoint, but no error amp (other than the NPN), so alas all my
-ve feedback "magic" stops working, so I have to:

a) temp-comp the setpoint (or NPN, but I want to keep I*Rs low), or

b) add some other form of current sensor, a T-stable reference and an
error amp, which I dont want to do.


so far the best I have come up with is placing a Vbe multiplier (using
the other transistor in the NPN's sot-323 package) in series with my
setpoint voltage. If I choose the Vbe multiplier scale factor to be the
reciprocal of the resistive divider formed from Vsetpoint to Rs, then
the divided-down scaled-up Vbe temperature change exactly (ish) cancels
out the dVbe of the NPN.

kinda:


Vsetpoint----[Vbe multiplier]---[R1]----+-----B of CE NPN
| \
0V--[Rs]--+---------------------[R2]----+ 0V
|
to switch Source (or E)


R1,R2 >> Rs

so I get:

Vbe1 - dVbe1 = (I*Rs)*R1/(R1+R2) + (Vs - K*(Vbe2 - dVbe2))*R2/(R1+R2)

and if the 2 BJTs are at the same temperature, then dVbe1 = dVbe2

so all I have to do is choose K = (R1+R2)/R1.


but it feels kinda icky.

Cheers
Terry


Can you post a schematic? I don't understand words very well ;-)

...Jim Thompson

Not really, I dont have access to ABSE. But I did send you an email.

Thanks,
Terry

Thanks, got it! Will observe in the morning.

...Jim Thompson

Later today. The eye folks added another test for this morning :-(

...Jim Thompson

 

[Eeyore]

That is ONE meaning, and NOT the only meaning, godammit.

Tell me the meaning you had in mind.

Graham

 

[Eeyore]

Nope.

Yes it is !

Graham

 

[krw]

And, according to Shakespeare, more dead lawyers.

Put even reasonable limits on torts and most lawyers will starve to
death. Two problems solved.

 

[John Fields]

Talking to utter dipshits that come off with stupid, meaningless
responses regarding national and international peace and security
isn't popular here in Usenet.


Then what the **** is your problem.

---
Basically, his problem is that he's an elitist and he can't stand it
when someone who he considers to be his inferior bests him.

That would be _any_ American as well as, I suspect, anyone not in
the British Commonwealth.

I can give you a good example from a while back, when he made the
silly mistake of thinking that the total current drawn from I/O's
could exceed the absolute maximum current allowed into or out of the
chip's power pins, and then tried every which way he could to get
off the hook instead of just admitting that he made a mistake.

Another problem is that he's so hungry for attention that he'll go
to any length to be able to start, or continue an argument.

 

[Eeyore]

Talking to utter dipshits that come off with stupid, meaningless
responses regarding national and international peace and security
isn't popular here in Usenet.


Then what the **** is your problem.

It seems to be your problem actually.

Graham

 

[Eeyore]

I can give you a good example from a while back, when he made the
silly mistake of thinking that the total current drawn from I/O's
could exceed the absolute maximum current allowed into or out of the
chip's power pins

You're a facetious idiot Fields.

Graham

 

[Eeyore]

Another problem is that he's so hungry for attention that he'll go
to any length to be able to start, or continue an argument.

That would be you actually.

Graham

 

[Phil Hobbs]

The real problem is $$$, a modern air force is appallingly expensive,
and we are pretty darned small - most big cities have more people than NZ.

Of course if anyone did invade us, they would discover that kiwis have
33x as many guns as our army (1 million c.f. 30,000), are extremely
inventive, and *really* dont like being pushed around.

Cheers
Terry

You make them sound like Virginians. So why are they so PC?

Cheers,

Phil "I Fled Canada" Hobbs

 

[Terry Given]

If that's not enough, there's always Gandalf...

Regards
Ian

I suspect shouting "you shall not pass" pretty much constitutes our
battle strtategy for the RNZAF

Cheers
Terry

 

[Terry Given]

France when they sank the Rainbow Warrior.

?! hows that NZ starting a war?

the really funny thing is, the French secret service got caught by the
NZ police department! Of course trade considerations meant we gave them
to france, who promptly punished them with a brief stay in a tropical
resort, followed by promotion.

For a long time there was jubilation every time we thumped the french at
rugby. But the french were the first to beat the world cup winning all
blacks; that night saying "vive la france" would have earned you a
serious beating; I narrowly escaped one for applauding (in a pub).

Cheers
Terry

 

[John Fields]

That would be you actually.

 

[Terry Given]

You make them sound like Virginians. So why are they so PC?

Cheers,

Phil "I Fled Canada" Hobbs

pass. perhaps its because we started out being so isolated that helping
each other was pretty much mandatory. much of PC is really more about
being nice, which is something we tend to go along with, to the point of
over-indulging the "land rights for gay black whales" PC zealots.
thankfully the therapy culture hasnt made much progress down here.

We are an on-going social experiment, but I think our novel strategy of
being nice to the original inhabitants is working pretty well (we had a
rough start, but still better than most places, and over the last 30yrs
or so have really got our act together).

Overall its a nice place to live. As long as you dont like crowds.

Cheers
Terry

 

[John Fields]

You're a facetious idiot Fields.

---
Wrong on both counts, dumbass.

The question was what your problem is and I explained what it is and
gave a good example to prove my point. Hardly facetious, and hardly
the rambling of an idiot. If you can prove that I'm wrong, then
let's hear the proof instead of your usual bullshit lies.

 

[Jim Thompson]

---
Wrong on both counts, dumbass.

The question was what your problem is and I explained what it is and
gave a good example to prove my point. Hardly facetious, and hardly
the rambling of an idiot. If you can prove that I'm wrong, then
let's hear the proof instead of your usual bullshit lies.

Notice how these leftist weenies ALWAYS fall back to calling names,
IDIOT being one of their favorites... it certainly is Win's favorite
;-)

BTW: This nasty winter... so nasty it must be proving global
something-or-other. Naaah! It's 34th in rank over the past 100
years.

Leftist weenies are the real IDIOTS ;-)

...Jim Thompson

 

[John Larkin]

Not to mention that the book Jurassic Park was made into a movie well
before Ann was a public figure.

...Jim Thompson

Don't annoy Homer with facts.

John