Maker Pro
Maker Pro

In search of a better line driver

C

Chris Carlen

Jan 1, 1970
0
Hi:

Here are some of the ways I have driven 50 ohm coax cables with TTL
level logic signals:

1. I have used 74HC14, 74AC14, and 74ACTQ14 devices to drive 50ohm
cables, with reasonably good results. I have tended to use one gate in
the package to drive several others in parallel, with a back terminating
resistor tuned to match the line Z, minus the output Z of the parallel
gates. This tends to produce some bumps after the edges that I'd like
to look better, mainly when driving an open line. Also, unless many
gates are used, lot variations in the output impedances of the gates can
cause substantial variations in edge quality from lot to lot.

I haven't tried using only a 74HC14 package with some parallel gates,
without one gate as pre-driver. Maybe this would be better. Ultimately
I want to not use such a large 14-pin package.

Also, I don't think it would be wise to use one 14-pin package to drive
multiple channels, since the ground and VCC bounces from one channel
feed a little bit into the others, except for very non-critical
applications.

2. I have used TC4426A MOSFET drivers as line drivers. They are very
good at this, but too slow for some purposes. I'd like to keep things
at least as fast or faster than HC CMOS.

3. Lately I have tried the Fairchild TinyLogic NC7WZ14 UHS dual Schmitt
inverters. I tied the two gates from one package in parallel, and again
used the back terminating R. I made a really nice layout on a 4-layer
board with a pair of 0.1uF 0805 bypass caps on either side of the package.

Boy this chip works great! It makes simply marvelous edges into even
the unterminated line.

But there is one problem. The thing is so small I can hardly solder it.
It sits on pads just a few tenths of millimeters per side. For the
first and only board on which I have used them, I had another tech.
assemble it who did a lowsy job, giving it back to me after apparently
no inspection. Today I bitched and moaned for an hour while I fixed the
poor solder joints. But they are almost impossible to solder well by
hand. Well, things might be better if I had the proper illuminated
magnifier, but I don't. Also, I was using 0.015" wire solder, which is
still too much to meter out consistently at this size.

Actually, I have a little general purpose line driver board I made using
the TC4426/7 chips, and had 100 of them assembled by an outside
contractor. It's only 0.65" x 0.75" and plugs into any board needing
line drivers, sparing me from re-evaluating the driver design for every
new situation. It simply includes everything: ESD and OVP protection,
LED driver, and the line driver. Expensive, but that's Ok for my lab
environment if it saves me time. These are cool, and I intend to do the
same perhaps with the Fairchild chips.

But if I could find a SO-8 packaged chip with similar specs to the
Fairchild UHS stuff, that would be almost ideal.

Are there any fast, 5V powered line driver chips in SO-8 or a package at
least a little larger than the 2.00mm x 1.25mm package of the Fairchild
UHS device?


Thanks for comments.


Good day!
 
S

Scott Stephens

Jan 1, 1970
0
I hope all the money you have enabled to be extorted from the American
taxpayer is eventually demanded from the consequences of your hacking.

Sincerely, in Jesus, or your favorite deity's name,

--
Scott

**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!

http://home.comcast.net/~scottxs/

**********************************
 
S

Stefan Heinzmann

Jan 1, 1970
0
Scott said:
I hope all the money you have enabled to be extorted from the American
taxpayer is eventually demanded from the consequences of your hacking.

Can you explain what that means? How did Chris enable any money
extortion? What has it got to do with the American taxpayer? How can you
demand anything from a consequence?
Sincerely, in Jesus, or your favorite deity's name,

What if I haven't got any favorite deity, or if it hasn't got a name?
 
S

Stefan Heinzmann

Jan 1, 1970
0
Chris said:
Here are some of the ways I have driven 50 ohm coax cables with TTL
level logic signals:

1. I have used 74HC14, 74AC14, and 74ACTQ14 devices to drive 50ohm
cables, with reasonably good results. I have tended to use one gate in
the package to drive several others in parallel, with a back terminating
resistor tuned to match the line Z, minus the output Z of the parallel
gates. This tends to produce some bumps after the edges that I'd like
to look better, mainly when driving an open line. Also, unless many
gates are used, lot variations in the output impedances of the gates can
cause substantial variations in edge quality from lot to lot.

Do you *need* to drive open (unterminated) lines? If so, you can hardly
avoid reflections, which will inevitably disturb the signal shape. The
only thing you can do then is to make the edges as slow as possible
without violating your timing requirements.

The best signal shape results from the use of a properly terminated
cable. The problem with that is that the back termination resistor forms
a voltage divider together with the termination on the other end of the
cable, so that the signal at the receiving end has only half the
amplitude of the signal at the output of the driver. If your driver chip
swings 5V, you'll get only 2.5V at the other end. That's only just TTL
compatible, so you loose noise margin.
I haven't tried using only a 74HC14 package with some parallel gates,
without one gate as pre-driver. Maybe this would be better. Ultimately
I want to not use such a large 14-pin package.

I don't believe it would make much difference.
Also, I don't think it would be wise to use one 14-pin package to drive
multiple channels, since the ground and VCC bounces from one channel
feed a little bit into the others, except for very non-critical
applications.

2. I have used TC4426A MOSFET drivers as line drivers. They are very
good at this, but too slow for some purposes. I'd like to keep things
at least as fast or faster than HC CMOS.

3. Lately I have tried the Fairchild TinyLogic NC7WZ14 UHS dual Schmitt
inverters. I tied the two gates from one package in parallel, and again
used the back terminating R. I made a really nice layout on a 4-layer
board with a pair of 0.1uF 0805 bypass caps on either side of the package.

Boy this chip works great! It makes simply marvelous edges into even
the unterminated line.

But there is one problem. The thing is so small I can hardly solder it.
It sits on pads just a few tenths of millimeters per side. For the
first and only board on which I have used them, I had another tech.
assemble it who did a lowsy job, giving it back to me after apparently
no inspection. Today I bitched and moaned for an hour while I fixed the
poor solder joints. But they are almost impossible to solder well by
hand. Well, things might be better if I had the proper illuminated
magnifier, but I don't. Also, I was using 0.015" wire solder, which is
still too much to meter out consistently at this size.

There are other ways to solder such parts. It involves using liquid
flux, wetting your soldering iron (with a broad tip) with a bit of
solder, and swiping it across the pins. The flux should prevent the
solder from bridging the pins.
Actually, I have a little general purpose line driver board I made using
the TC4426/7 chips, and had 100 of them assembled by an outside
contractor. It's only 0.65" x 0.75" and plugs into any board needing
line drivers, sparing me from re-evaluating the driver design for every
new situation. It simply includes everything: ESD and OVP protection,
LED driver, and the line driver. Expensive, but that's Ok for my lab
environment if it saves me time. These are cool, and I intend to do the
same perhaps with the Fairchild chips.

But if I could find a SO-8 packaged chip with similar specs to the
Fairchild UHS stuff, that would be almost ideal.

Are there any fast, 5V powered line driver chips in SO-8 or a package at
least a little larger than the 2.00mm x 1.25mm package of the Fairchild
UHS device?

There's a little bit of extra information needed first. What levels do
you want on the cable? Do you want to be able to receive the signal on
the other end with an ordinary TTL input (that is 0..0.8V means 0 and
2.0..5V means 1)? What signal rise and fall times do you need? What are
the cable lengths you need to support, and at what loss? Is it necessary
to support unterminated cables?
 
R

Rene Tschaggelar

Jan 1, 1970
0
Chris said:
Hi:

Here are some of the ways I have driven 50 ohm coax cables with TTL
level logic signals:

Somehow you forgot to tell us the speed requirements.
Or did I read too quick ?
Nevertheless. Termination may be a problem.
I'd recommend the 74F3037 from Philips in the SO16 case.
Does 2.5ns to 2.8V into 50 Ohms with 20 Ohms in series.

Rene
 
J

John Larkin

Jan 1, 1970
0
Do you *need* to drive open (unterminated) lines? If so, you can hardly
avoid reflections, which will inevitably disturb the signal shape. The
only thing you can do then is to make the edges as slow as possible
without violating your timing requirements.

If you drive a 50 ohm coax from a 50 ohm source (ie, logic gate +
source-termination resistor) with a 5-volt step, you'll get a clean
5-volt step at the unterminated far end; the load sees no evidence of
reflections. The advantage of this is that the driver chip sees a 100
ohm load (local 50 ohm source termination + coax) so makes cleaner,
faster edges with less ground bounce and other abberations. Power
dissipation is much reduced, too.

John
 
S

Stefan Heinzmann

Jan 1, 1970
0
John said:
If you drive a 50 ohm coax from a 50 ohm source (ie, logic gate +
source-termination resistor) with a 5-volt step, you'll get a clean
5-volt step at the unterminated far end; the load sees no evidence of
reflections. The advantage of this is that the driver chip sees a 100
ohm load (local 50 ohm source termination + coax) so makes cleaner,
faster edges with less ground bounce and other abberations. Power
dissipation is much reduced, too.

You're right, you would only see the intermediate voltage somewhere
along the cable, but not at the end. So it would be viable for a
point-to-point communication.
 
C

Chris Carlen

Jan 1, 1970
0
Stefan said:
Do you *need* to drive open (unterminated) lines? If so, you can hardly
avoid reflections, which will inevitably disturb the signal shape. The
only thing you can do then is to make the edges as slow as possible
without violating your timing requirements.

John Larkin responded adequately to this below.
There are other ways to solder such parts. It involves using liquid
flux, wetting your soldering iron (with a broad tip) with a bit of
solder, and swiping it across the pins. The flux should prevent the
solder from bridging the pins.

Yeah, I should really try some different tips, or maybe get one of the
Pace "mini-wave" tips. I also need a proper illuminated stereo magnifier.

I have used the manner you describe for 100-pin TQFP type packages, and
had little trouble. The pins were closer. Actually, I let some bridge,
and just wicked a little off later. This little 6-pin package however
has a relatively wide lead spacing.
There's a little bit of extra information needed first. What levels do
you want on the cable? Do you want to be able to receive the signal on
the other end with an ordinary TTL input (that is 0..0.8V means 0 and
2.0..5V means 1)? What signal rise and fall times do you need? What are
the cable lengths you need to support, and at what loss? Is it necessary
to support unterminated cables?

Yes, TTL input on the other end. So I want to get at least 2.4V into a
50-ohm terminator, and at least 4.5V into an unterminated end. I need
to be able to handle terminated and unterminated ends. The reasons are
complex, because this driver design must serve many applications in a
lab environment where all sorts of things may be at the receiving end.
Most can deal with the TTL levels, but some are quirky and need more
than 2.4V. I think I have some stuff that is incorrectly labelled "TTL"
compatible but really has CMOS 2.5V thresholds. Thus, I need clean
transitions even if the line is unterminated to get the full close to 5V
swing. Hence the back terminated design. There is no need in a case
like this to have clean edges at intermediate points in the cable. Of
course the reflections will be visible in the middle of the cable. So
mostly these are point-to-point connections. In cases where there are
daisy-chained connections, I have instructed my users to terminate the
lines, and use short stubs or only T fittings to tap the lines.

No matter what I say, they still wire things up all wrong!


Anyway, for the rest of the specs, I'd like to have about <10ns rise and
fall times for 50 ft. or less cables, and the driver should have <40ns
of propagation delay, with as symmetric as possible propagation delays.



Ok, thanks for the input Stefan.


Have a good day!
 
C

Chris Carlen

Jan 1, 1970
0
Rene said:
Somehow you forgot to tell us the speed requirements.
Or did I read too quick ?
Nevertheless. Termination may be a problem.
I'd recommend the 74F3037 from Philips in the SO16 case.
Does 2.5ns to 2.8V into 50 Ohms with 20 Ohms in series.

Rene


What would be really cool is an XOR line driver, so it could be
selectable inverting or non-inverting without changing the gate delay.

Programmable slew rate would be nice too.

:)


Thanks for the input! I think I may just stick with the Fairchilds' and
learn how to solder them well or contract the assembly. I'm getting a
bit tired of assembly anyway, and don't have time for it anymore with
all the projects that need attention.

Good day!
 
S

Stefan Heinzmann

Jan 1, 1970
0
Chris said:
Stefan Heinzmann wrote: [...]
There's a little bit of extra information needed first. What levels do
you want on the cable? Do you want to be able to receive the signal on
the other end with an ordinary TTL input (that is 0..0.8V means 0 and
2.0..5V means 1)? What signal rise and fall times do you need? What
are the cable lengths you need to support, and at what loss? Is it
necessary to support unterminated cables?


Yes, TTL input on the other end. So I want to get at least 2.4V into a
50-ohm terminator, and at least 4.5V into an unterminated end. I need
to be able to handle terminated and unterminated ends. The reasons are
complex, because this driver design must serve many applications in a
lab environment where all sorts of things may be at the receiving end.
Most can deal with the TTL levels, but some are quirky and need more
than 2.4V. I think I have some stuff that is incorrectly labelled "TTL"
compatible but really has CMOS 2.5V thresholds. Thus, I need clean
transitions even if the line is unterminated to get the full close to 5V
swing. Hence the back terminated design. There is no need in a case
like this to have clean edges at intermediate points in the cable. Of
course the reflections will be visible in the middle of the cable. So
mostly these are point-to-point connections. In cases where there are
daisy-chained connections, I have instructed my users to terminate the
lines, and use short stubs or only T fittings to tap the lines.

No matter what I say, they still wire things up all wrong!


Anyway, for the rest of the specs, I'd like to have about <10ns rise and
fall times for 50 ft. or less cables, and the driver should have <40ns
of propagation delay, with as symmetric as possible propagation delays.

Hm, I realize that you have put in more consideration than I thought. I
may not have much to contribute in this case. I briefly had thought
about ATE pin drivers, but they're most likely much too expensive for
what you try to do.

If you get better results with Tiny Logic chips then I guess this is
because the small package makes good decoupling easier. If that turns
out to be the reason then you may have to bite the bullet and invest in
soldering equipment ;-)

What has puzzled me in the past is why the low voltage logic series, for
example 74LVC, which are specified for supply voltages up to 3.6V, have
some family members that are specified for 5V operation. So for example
the 74LVC3G04, which is specified for 5V operation, whereas the 74LVC04A
isn't.
 
J

John Larkin

Jan 1, 1970
0
Hi:

Here are some of the ways I have driven 50 ohm coax cables with TTL
level logic signals:

1. I have used 74HC14, 74AC14, and 74ACTQ14 devices to drive 50ohm
cables, with reasonably good results. I have tended to use one gate in
the package to drive several others in parallel, with a back terminating
resistor tuned to match the line Z, minus the output Z of the parallel
gates. This tends to produce some bumps after the edges that I'd like
to look better, mainly when driving an open line. Also, unless many
gates are used, lot variations in the output impedances of the gates can
cause substantial variations in edge quality from lot to lot.

I haven't tried using only a 74HC14 package with some parallel gates,
without one gate as pre-driver. Maybe this would be better. Ultimately
I want to not use such a large 14-pin package.

Also, I don't think it would be wise to use one 14-pin package to drive
multiple channels, since the ground and VCC bounces from one channel
feed a little bit into the others, except for very non-critical
applications.

2. I have used TC4426A MOSFET drivers as line drivers. They are very
good at this, but too slow for some purposes. I'd like to keep things
at least as fast or faster than HC CMOS.

3. Lately I have tried the Fairchild TinyLogic NC7WZ14 UHS dual Schmitt
inverters. I tied the two gates from one package in parallel, and again
used the back terminating R. I made a really nice layout on a 4-layer
board with a pair of 0.1uF 0805 bypass caps on either side of the package.

Boy this chip works great! It makes simply marvelous edges into even
the unterminated line.

But there is one problem. The thing is so small I can hardly solder it.
It sits on pads just a few tenths of millimeters per side. For the
first and only board on which I have used them, I had another tech.
assemble it who did a lowsy job, giving it back to me after apparently
no inspection. Today I bitched and moaned for an hour while I fixed the
poor solder joints. But they are almost impossible to solder well by
hand. Well, things might be better if I had the proper illuminated
magnifier, but I don't. Also, I was using 0.015" wire solder, which is
still too much to meter out consistently at this size.

Actually, I have a little general purpose line driver board I made using
the TC4426/7 chips, and had 100 of them assembled by an outside
contractor. It's only 0.65" x 0.75" and plugs into any board needing
line drivers, sparing me from re-evaluating the driver design for every
new situation. It simply includes everything: ESD and OVP protection,
LED driver, and the line driver. Expensive, but that's Ok for my lab
environment if it saves me time. These are cool, and I intend to do the
same perhaps with the Fairchild chips.

But if I could find a SO-8 packaged chip with similar specs to the
Fairchild UHS stuff, that would be almost ideal.

Are there any fast, 5V powered line driver chips in SO-8 or a package at
least a little larger than the 2.00mm x 1.25mm package of the Fairchild
UHS device?


Thanks for comments.


Good day!


My favorite is the Onsemi NL37WZ16US, a triple buffer, using all three
sections in parallel. If you run it from 6 volts and use, say, 10 ohms
in series, it puts almost 5 volts into 50 ohms in about 500 ps. Or
source terminated, powered from 5, it will deliver about 4.5 at the
open end.

But it's a US8 package. To hand solder, wet the pins with liquid flux,
blob a tiny bit of solder on your iron, and touch each pin; solder
will wick from the tip to the pin and pad.

John
 
S

Scott Stephens

Jan 1, 1970
0
Stefan said:
Can you explain what that means? How did Chris enable any money
extortion? What has it got to do with the American taxpayer? How can you
demand anything from a consequence?

He works for some fed lab. Our government thinks it is OK, under the
guise of 'promoting the general welfare' to extort money from taxpayers
(theft), squander a little on 'research', while filching the lions'
share to pay corporate contributors with government contracts who
kick-back 'campaign contribution' bribes to politicians.

Lawful government only acts to prevent crimes against life, property and
freedom:
http://www.freeaudio.org
http://bastiat.org/en/the_law.html

There is something known as "Opportunity Cost".

The feds demand I pay them to research solar cells, windmills, and space
stations, so 'spin-offs' will make our lives better. If the private
sector undertook such research it would be done efficiently and
effectively, or not at all.

The market place punishes ineffectiveness. Government rewards it.
Business must compete to give you the most value at the least profit and
waste to stay in business. Government gives you the least value you can
tolerate at the greatest expense, because it is a monopoly. Not only a
monopoly for the research it extorts money for, but most aggregiously, a
monopoly on violence to extort money by force.
What if I haven't got any favorite deity, or if it hasn't got a name?

What is your value? If there is any meaning or value for you
individually, perhaps it is your very own life? And by what virtues do
you attain this value, your life? How about such values as self-esteem,
reason and productivity?

Why aren't you manufacturing crank? It is very profitable, and with
electronics and a bit of savvy for anonymity with drop sites and pagers,
you're not likely to get caught, even though your minions will rot in
jail, and customers get addicted, sick and dead.

Self esteem no doubt. You want to be productive, creative, because you
love life. Otherwise, you wouldn't be here. Throughout history diverse
cultures developed religions and the concept of *God* as a spirit, an
ideal of creativity and life, even the means to attain the values and
virtues through service and prayer. Perhaps the name of your god, what
you live for, is 'creativity' or 'life'?

On the other hand, perhaps you are just doing what you watched others
do, what your father did, because you don't think or are very aware.

***

Perhaps God knows what is in our presidents heart. I don't know, I've
heard too many cheap political excuses to believe any more excuses. Such
as the "free market" excuses why Bush passes by California Samaritans,
robbed and pushed into a gamed-commodities market ditch by his fellow
Texan and contributor Ken Lay, CEO of Enron.

George Bush admonishes us to "Love our neighbor as we want to be loved".
Like Jesus' told him.

Problem is, we are not Brother Bush's neighbors. Brother Bush's
neighbors are all worth over $5 million, as are Comrade Kerry's neighbors.

"Perfectly Legal:The Covert Campaign to Rig our Tax System to Benefit
the Super Rich- and Cheat Everyone Else
by David Cay Johnston

http://www.perfectlylegalthebook.com/sample.htm
http://www.booknotes.org/Transcript/?ProgramID=1776 "

We are peasants, forced and expected to tolerate double-standards and
live for an aristocracy of fascists or communists.

An acquaintance defended the government's policies by stating that what
government was to me was not what it was to him. He was happy with what
government did with his money. Kind of like saying "life is hard".
"Tough luck". "Dog-eat-dog world".

Our dear Christian president tells us to treat others as we want to be
treated. To volunteer to serve the collective. While I am looted and
told, "life is hard".

***

I try not to get personal, I envy Chris Carlen. I wish the feds paid me
to learn and build stuff, rather than having paid me to squander
extorted taxpayer money, and console myself with not being as miserable
as other sick and miserable people employed at the sick, miserable
national lab I worked at.

I should have just said, "Mr. Carlen, God damn your sick, mean, evil
government employer", but a few drinks fog the mind.

--
Scott

**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!

http://home.comcast.net/~scottxs/

**********************************
 
S

Stefan Heinzmann

Jan 1, 1970
0
Scott said:
He works for some fed lab. Our government thinks it is OK, under the
guise of 'promoting the general welfare' to extort money from taxpayers
(theft), squander a little on 'research', while filching the lions'
share to pay corporate contributors with government contracts who
kick-back 'campaign contribution' bribes to politicians.

Lawful government only acts to prevent crimes against life, property and
freedom:
http://www.freeaudio.org
http://bastiat.org/en/the_law.html

There is something known as "Opportunity Cost".

The feds demand I pay them to research solar cells, windmills, and space
stations, so 'spin-offs' will make our lives better. If the private
sector undertook such research it would be done efficiently and
effectively, or not at all.

The market place punishes ineffectiveness. Government rewards it.
Business must compete to give you the most value at the least profit and
waste to stay in business. Government gives you the least value you can
tolerate at the greatest expense, because it is a monopoly. Not only a
monopoly for the research it extorts money for, but most aggregiously, a
monopoly on violence to extort money by force.

Hmm, I see where you're getting at. I beg to differ, however, although
I'm not keen on discussing this here, as it is OT. Just one argument,
though. In my opinion, it is one of the most important (and often
neglected) duties of government to uphold and enforce conditions that
allow the market forces to prevail. Left alone, the market has a
tendency to drift towards cartels and monopolies. The result is
certainly not increased efficiency. Markets need rules, just like other
aspects of a community. Quite frequently, government imposed rules
/increase/ efficiency, which would not easily come about if the market
were left alone, for example by enforcing standards (mains voltages,
rail gages, radio spectrum usage, ...). So the question rather is one of
balance, not of principle.

Now, whether Chris' employer is a waste of (taxpayer's) money or not is
something I can't tell, and it isn't my tax money anyway.
What is your value? If there is any meaning or value for you
individually, perhaps it is your very own life? And by what virtues do
you attain this value, your life? How about such values as self-esteem,
reason and productivity?

Why aren't you manufacturing crank? It is very profitable, and with
electronics and a bit of savvy for anonymity with drop sites and pagers,
you're not likely to get caught, even though your minions will rot in
jail, and customers get addicted, sick and dead.

Self esteem no doubt. You want to be productive, creative, because you
love life. Otherwise, you wouldn't be here. Throughout history diverse
cultures developed religions and the concept of *God* as a spirit, an
ideal of creativity and life, even the means to attain the values and
virtues through service and prayer. Perhaps the name of your god, what
you live for, is 'creativity' or 'life'?

If your notion of god is that broad, fair enough. That's not what is
usually being associated with this word, at least in our "western"
culture. You're bound to be misunderstood that way. Such a broad
definition of a god usually comes with the notion that atheism is just
another form of religion, which brushes aside the rather fundamental
differences.
On the other hand, perhaps you are just doing what you watched others
do, what your father did, because you don't think or are very aware.

That's how it started. My awareness and thought developed over time.
Perhaps God knows what is in our presidents heart. I don't know, I've
heard too many cheap political excuses to believe any more excuses. Such
as the "free market" excuses why Bush passes by California Samaritans,
robbed and pushed into a gamed-commodities market ditch by his fellow
Texan and contributor Ken Lay, CEO of Enron.

George Bush admonishes us to "Love our neighbor as we want to be loved".
Like Jesus' told him.

Problem is, we are not Brother Bush's neighbors. Brother Bush's
neighbors are all worth over $5 million, as are Comrade Kerry's neighbors.

"Perfectly Legal:The Covert Campaign to Rig our Tax System to Benefit
the Super Rich- and Cheat Everyone Else
by David Cay Johnston

http://www.perfectlylegalthebook.com/sample.htm
http://www.booknotes.org/Transcript/?ProgramID=1776 "

We are peasants, forced and expected to tolerate double-standards and
live for an aristocracy of fascists or communists.

An acquaintance defended the government's policies by stating that what
government was to me was not what it was to him. He was happy with what
government did with his money. Kind of like saying "life is hard".
"Tough luck". "Dog-eat-dog world".

Our dear Christian president tells us to treat others as we want to be
treated. To volunteer to serve the collective. While I am looted and
told, "life is hard".

As he isn't my president, I am probably not qualified to comment. Given
the impact the US have on the rest of the world it nevertheless matters
to me. And I have learned to start worrying when leaders invoke
religious icons and feelings. GWB has done this in the run-up to the war
in Iraq (he even spoke of a crusade, a particularly damaging term when
you are dealing with muslims). It is sad to see the fruits of this now.
The world does not appear to me to be a safer place now. The result is a
far greater drain on the assets of the US nation IMHO than funding of
federal labs. And I mean both material and immaterial assets.
I try not to get personal, I envy Chris Carlen. I wish the feds paid me
to learn and build stuff, rather than having paid me to squander
extorted taxpayer money, and console myself with not being as miserable
as other sick and miserable people employed at the sick, miserable
national lab I worked at.

I should have just said, "Mr. Carlen, God damn your sick, mean, evil
government employer", but a few drinks fog the mind.

If they washed down your anger the drinks were well employed ;-)
 
S

Scott Stephens

Jan 1, 1970
0
Hmm, I see where you're getting at. I beg to differ, however, ....
Just one argument, though. In my opinion, it is one of the most important (and often
neglected) duties of government to uphold and enforce conditions that
allow the market forces to prevail. Left alone, the market has a
tendency to drift towards cartels and monopolies. The result is
certainly not increased efficiency. Markets need rules, just like other
aspects of a community. Quite frequently, government imposed rules
/increase/ efficiency, which would not easily come about if the market
were left alone, for example by enforcing standards (mains voltages,
rail gages, radio spectrum usage, ...). So the question rather is one of
balance, not of principle.

Agreed. Police are necessary to encourage honest people and corporations
to be honest, by discouraging desperate, immoral opportunism by the weak.
That's how it started. My awareness and thought developed over time.

I think that is pretty much how all of us get started. But what do we do
with that awareness and thought? Is it developed, so that we think and
act according to reason to become self-respecting and productive, or
suppressed by shame as we are enslaved by sick bureaucrats which
manipulate us with guilt and fear, to the end we hide from ourselves in
self-denial, and become the tools of evil-doers?
As he isn't my president, I am probably not qualified to comment. Given
the impact the US have on the rest of the world it nevertheless matters
to me.

I should think so. Especially since future president Kerry is using
"world opinion" to sell himself to the American public, and will be
influencing your government. Apparently the Democratic Party thinks
Americans can't kill predators or go to war without international
cheerleaders. Its a guilt and shame thing. War is OK if the French say so.

And our bribed government will export our industry and jobs to you (if
you'll do the work cheaply enough) even if you enslave children, ignore
and evade safety and health regulations, and spend the money subverting
the causes of freedom and democracy. Was it Marx or Lenin that said
capitalists are suicidal? Our capitalists are bribing our politicians to
outsource the construction of the instruments of our national execution.

We have to compete with Chinese, that run gulags and sell body-parts of
their victims. That's what tariffs are for. Just as we tax industry that
pollutes to pay for the damage, foreign nations that devalue life
deserve similar penalties.

And I have learned to start worrying when leaders invoke
religious icons and feelings. GWB has done this in the run-up to the war
in Iraq (he even spoke of a crusade, a particularly damaging term when
you are dealing with muslims).

I noticed that too. It is scary, but fundamentalist Islam is far, far
more scary. They murder their bleeding-heart wussy liberals, whereas we
elect them to office after our fundamentalists fail us and we tire of
their excuses. The American public turns to one political party for
justice, receives instead fraud and injustice, then elects a politician
from the opposing criminal party.
The world does not appear to me to be a safer place now. The result is a
far greater drain on the assets of the US nation IMHO than funding of
federal labs. And I mean both material and immaterial assets.

One sin does not sanction another. Wasting money and opportunity cost is
wasted money and opportunity. I'd rather see my tax money fixing our
slums than Iraq slums, fixing our own homes before we set out to fix our
neighbor's house. But extorting tax money is theft and forced servitude,
whether it is spent on the poor or a palace, the money was stolen and
injustice compounded. Though the government excuses theft by the refusal
of men to share with one another, then appeals to popularity and
consensus as a definition of 'social' justice, democratic kleptocrasy
simply multiplies injustice.
If they washed down your anger the drinks were well employed ;-)

Just a brief vacation from an ugly business of living. Awareness and
acceptance take time, and demand action and change.

--
Scott

**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!

http://home.comcast.net/~scottxs/

**********************************
 
C

Chris Carlen

Jan 1, 1970
0
John said:
My favorite is the Onsemi NL37WZ16US, a triple buffer, using all three
sections in parallel. If you run it from 6 volts and use, say, 10 ohms
in series, it puts almost 5 volts into 50 ohms in about 500 ps. Or
source terminated, powered from 5, it will deliver about 4.5 at the
open end.

But it's a US8 package. To hand solder, wet the pins with liquid flux,
blob a tiny bit of solder on your iron, and touch each pin; solder
will wick from the tip to the pin and pad.

John

Thanks for the new part number to look into. Uhm I see it is in another
subatomic package.

Good grief that's probably too fast. I actually tried the Fairchild UHS
gadget on your suggestion. I really like it, except for the smallness.
I suppose I'll get used to it, and ask my boss to let me buy a
magnifier and a better iron. I should also make my SMD pads extend out
a little farther than the ones I am using.

Any programmable slew rate drivers out there?



Good day!
 
N

Nico Coesel

Jan 1, 1970
0
Chris Carlen said:
Hi:

Here are some of the ways I have driven 50 ohm coax cables with TTL
level logic signals:

1. I have used 74HC14, 74AC14, and 74ACTQ14 devices to drive 50ohm
cables, with reasonably good results. I have tended to use one gate in
the package to drive several others in parallel, with a back terminating

You could take a look into RS485 drivers. These can drive 50 Ohm loads
(2 times 100 Ohms in parallel on the bus = 50Ohm load) and these are
also available in several slew rate limited editions... ehmmm versions
that is.
 
J

John Larkin

Jan 1, 1970
0
Thanks for the new part number to look into. Uhm I see it is in another
subatomic package.


Get used to it. They're getting nothing but smaller.

Good grief that's probably too fast. I actually tried the Fairchild UHS
gadget on your suggestion. I really like it, except for the smallness.
I suppose I'll get used to it, and ask my boss to let me buy a
magnifier and a better iron. I should also make my SMD pads extend out
a little farther than the ones I am using.


Get one of these if you can. They are astounding optics, about $2000
and more than worth it.

http://www.visioneng.com/mantis/index.htm

Any programmable slew rate drivers out there?

I wish!

The world needs a great pin driver: easily programmed Vh and Vl, swing
from at least -4 to +10, clean edges with sharp corners, slew rate 4.5
v/ns into 50 ohms [1]; programmable slew would be nice.

John

[1] anybody know why 4.5?
 
C

Chris Carlen

Jan 1, 1970
0
John said:
Get one of these if you can. They are astounding optics, about $2000
and more than worth it.

http://www.visioneng.com/mantis/index.htm


Hi John, thanks for the link.

Do you actually solder under this thing, or just use it for inspection?
I would be concerned about getting the optics mucked up from soldering
smoke, though I suppose that could be dealt with by using a good bench
flow type fume extractor.

Good day!



--
____________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
[email protected]
 
K

krw

Jan 1, 1970
0
You're right, you would only see the intermediate voltage somewhere
along the cable, but not at the end. So it would be viable for a
point-to-point communication.

It also works for multi-drop communication over "short" distances (See:
"PCI" and "reflected wave switching"). One samples away from the step.
 
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