Photodiode case

[Jim Thompson]

[snip]

My long beard is gone. But I have adopted the
Bruce Willis / Hollywood look, where 2 to 3 days
is optimum. Actually, for me, this translates
into fluctuating between 0 and 15 days.

Bwahahahahaha! And I thought you had no sense of humor.

We BOTH sure look like Bruce Willis don't we ?

(I use the shortest setting on my beard clippers... probably about
1/8"... I'd do the same to the hair on my head but, as Joerg notes,
SWMBO objects to such a severe treatment

...Jim Thompson

Wow, I had you both pegged as more like Willie Nelson.

Cheers,

Phil Hobbs

I'm not into ratty-looking beards.

...Jim Thompson

 

[Jim Thompson]

[snip]
My long beard is gone. But I have adopted the
Bruce Willis / Hollywood look, where 2 to 3 days
is optimum. Actually, for me, this translates
into fluctuating between 0 and 15 days.


Bwahahahahaha! And I thought you had no sense of humor.

We BOTH sure look like Bruce Willis don't we ?

(I use the shortest setting on my beard clippers... probably about
1/8"... I'd do the same to the hair on my head but, as Joerg notes,
SWMBO objects to such a severe treatment

...Jim Thompson

Wow, I had you both pegged as more like Willie Nelson.

Nah, then they'd both be driving a big truck with mud flaps and them big
errialls ;-)

Or at least a Harley like them's guys out here who performed with him at
times:
http://dixonmayfair.com/news/news050407.html

I DO own a pick-em-up truck (though it's a Frontier ;-)

...Jim Thompson

 

[Phil Hobbs]

If the voltage noise of the bootstrap follower amplifier
is the same as the voltage noise of the transimpedance
opamp, there's not only no overall noise benefit, there's
a small penalty. Yes. Although in many cases I imagine
there can be a substantial practical bandwidth improvement
without requiring an otherwise highly-complex circuit.
Perhaps that was their appeal in those old tube days.

In the happy case of the bf862, which is easy to use in a
high-performance follower bootstrap, its noise is much less
than available JFET opamps, and it equals or approaches a
BJT's performance without the dynamic-range limitations.


Right, fine, but for us a 10:1 or even 100:1 limit would
still be a special case. For the common case of single-shot
non-repetitive events, even though the weak signals may not
be above their shot noise, it's still necessary to measure
them and to know where zero is, as you agree, right?

If that's your measurement situation, sure. Generally I'm providing at
least one laser beam, so can usually know where I am, more or less.
Sometimes I need to know the absolute photocurrent, in which case I
usually use a slow LPF on the other end of the diode where it doesn't
get in the way.

For really wide range things I like to use diodes as feedback elements
(diode-connected transistors really, of course). Diodes have noise
temperatures of half the ambient (150K at room temperature), and if you
use a bunch of them in series, the gain and load resistance adjust
themselves so you can stay in the shot noise limit over a much wider
dynamic range than you can with resistors. Another nice approach is
just to stuff a photodiode into the input of a nice quiet UHF amp--Miteq
sells some that get down to 25K noise temperature at 300K ambient, and
10K at 77K ambient.

I actually just ordered some BF862s and OPA657s to try out--with all the
device work I've been doing, I haven't designed a front end in ages, and
I need to do a few for the second edition anyway. I don't use anything
like the same variety of parts as you do in AoE, but still, I can't very
well go on singing the praises of an op amp that went out of production
in 2004 (the LF357).

(I just got back a few sample chips that I hope will be the first real
photovoltaic antenna-coupled tunnel junctions. Gold antennas and
yttrium / nickel oxide / platinum TJs. Odds of them working: probably 30%.)

Cheers,

Phil Hobbs

 

[John Larkin]

Jim Thompson wrote:
[snip]
My long beard is gone. But I have adopted the
Bruce Willis / Hollywood look, where 2 to 3 days
is optimum. Actually, for me, this translates
into fluctuating between 0 and 15 days.


Bwahahahahaha! And I thought you had no sense of humor.

We BOTH sure look like Bruce Willis don't we ?

(I use the shortest setting on my beard clippers... probably about
1/8"... I'd do the same to the hair on my head but, as Joerg notes,
SWMBO objects to such a severe treatment

...Jim Thompson

Wow, I had you both pegged as more like Willie Nelson.

Nah, then they'd both be driving a big truck with mud flaps and them big
errialls ;-)

Or at least a Harley like them's guys out here who performed with him at
times:
http://dixonmayfair.com/news/news050407.html

Scary, very scary. I've ridden on a motorcycle once in my life--it was
a Yamaha RD400 (two-stroke) and I was on the back. Problem was, the
other guy was about half my size, and the bike went where *I* leaned,
not where he did. We never even got out of the parking lot.

I've had 13 motorcycle crashes on the street, about half involving
cars, and literally hundreds in the dirt, a few of which involved
trees. My wife is a speech pathologist who has worked on too many guys
who will be goofy or veggies for the rest of their lives, so I sold my
bikes. Besides, the drivers are way too scary these days.

But I still ski.

John

 

[Winfield Hill]

I actually just ordered some BF862s and OPA657s to try out--with all the
device work I've been doing, I haven't designed a front end in ages, and
I need to do a few for the second edition anyway. I don't use anything
like the same variety of parts as you do in AoE, but still, I can't very
well go on singing the praises of an op amp that went out of production
in 2004 (the LF357).

Our 1988 2nd edition jellybean JFET opamp was the LF411,
which is basically the unity-gain-compensated low-supply-
current regular-speed, newer version of the LF357. When
we looked for a replacement jellybean for the 3rd edition,
after going all around, we came back to almost the same
part: either an LF411 or the LF412 dual version, and the
LF412A for better accuracy. This was because the newer,
interesting opamps can't be used with +/-15V supplies.
Yes, we'll have a newer +/-5V-supply jellybean opamp,
but the LF412 nicely fits the bill for a routine opamp.
Either that or maybe the TL082, etc., except it's really
an inferiour amplifier to the LF412. I see the LF353 is
also rather cheap and well stocked. So there really has
not been much evolution in 20 years!

(I just got back a few sample chips that I hope will be the first real
photovoltaic antenna-coupled tunnel junctions. Gold antennas and
yttrium / nickel oxide / platinum TJs. Odds of them working: probably 30%.)

Now, THAT sounds like fun! Good luck with it.

 

[Phil Hobbs]

Our 1988 2nd edition jellybean JFET opamp was the LF411,
which is basically the unity-gain-compensated low-supply-
current regular-speed, newer version of the LF357. When
we looked for a replacement jellybean for the 3rd edition,
after going all around, we came back to almost the same
part: either an LF411 or the LF412 dual version, and the
LF412A for better accuracy. This was because the newer,
interesting opamps can't be used with +/-15V supplies.
Yes, we'll have a newer +/-5V-supply jellybean opamp,
but the LF412 nicely fits the bill for a routine opamp.
Either that or maybe the TL082, etc., except it's really
an inferiour amplifier to the LF412. I see the LF353 is
also rather cheap and well stocked. So there really has
not been much evolution in 20 years!

Well, I've come to the same conclusion, but you used a much more
creditable method...I just have drawers full of old parts.

The 411/412 and 353 are noisy like the 351, iirc. The 356/357 were
quieter. The good behaviour, +- 15V supplies, and (especially) the 2 pF
input capacitance were extra nice, even if the Vos performance wasn't
that great. The +-15V is really important for dynamic range--I hate
losing 9-10 dB by using +-5, and losing 15 dB for the privilege of using
+5/0 genuinely stinks. (The old +- 150V tube op amp supplies look
better all the time!)

Now, THAT sounds like fun! Good luck with it.

Thanks. I'll know tomorrow whether the I-V characteristics are any
good. If they are, we'll try making some waveguide-coupled devices in
November. Our Ni/NiO/Ni devices have responsivities about 0.08 A/W at
present, and there are lots of efficiency tweaks to go, but they need
100 mV of bias. We're trying for a 100x decrease in overall I/O power
for computers--we hope to show that you can get to 40 uW/(Gb/s) end to
end, including laser power. The problem is that it's really hard to
simulate the device performance, due to multiple length scales--the
tunnel junction is about 2 microns long by 400 angstroms wide by 25
angstroms thick, and so to get any resolution down in the junction
region, you have to do simulations in 30 GB of memory that take days to
run.

Cheers,

Phil Hobbs

 

[Richard The Dreaded Libertarian]

Wow, I had you both pegged as more like Willie Nelson.

Actually, Jim looks more like Dick Cheney, but fatter. ;-)

Cheers!
Rich

 

[Rich Grise]

Scary, very scary. I've ridden on a motorcycle once in my life--it was
a Yamaha RD400 (two-stroke) and I was on the back. Problem was, the
other guy was about half my size, and the bike went where *I* leaned,
not where he did. We never even got out of the parking lot.

It was your fault. As passenger, you're not supposed to do any leaning
at all - you're supposed to sit there and let the driver drive the bike,
while you simply ride it. From his POV, you are part of the load, and
when he compensates for your mass, he expects you to stay put relative
to the bike.

On the other hand, on bicycles I've nearly gotten myself killed more
times than I can count.

That only means that you've never learned to ride a bike properly/safely.

Thanks,
Rich

 

[Joerg]

Jim Thompson wrote:
[snip]
My long beard is gone. But I have adopted the
Bruce Willis / Hollywood look, where 2 to 3 days
is optimum. Actually, for me, this translates
into fluctuating between 0 and 15 days.

Bwahahahahaha! And I thought you had no sense of humor.

We BOTH sure look like Bruce Willis don't we ?

(I use the shortest setting on my beard clippers... probably about
1/8"... I'd do the same to the hair on my head but, as Joerg notes,
SWMBO objects to such a severe treatment

...Jim Thompson
Wow, I had you both pegged as more like Willie Nelson.

Nah, then they'd both be driving a big truck with mud flaps and them big
errialls ;-)

Or at least a Harley like them's guys out here who performed with him at
times:
http://dixonmayfair.com/news/news050407.html

I DO own a pick-em-up truck (though it's a Frontier ;-)

That don't count. Mine's also a "Rice Jeep".

What I meant was this kind:
http://www.toughcountry.com/dodge/pages/21_dodge_jpg.htm

 

[Rich Grise]

Phil Hobbs wrote:
Jim Thompson wrote:
On Tue, 30 Oct 2007 11:47:38 -0700, Winfield Hill <[email protected]>
[snip]
My long beard is gone. But I have adopted the
Bruce Willis / Hollywood look, where 2 to 3 days
is optimum. Actually, for me, this translates
into fluctuating between 0 and 15 days.

Bwahahahahaha! And I thought you had no sense of humor.

We BOTH sure look like Bruce Willis don't we ?

(I use the shortest setting on my beard clippers... probably about
1/8"... I'd do the same to the hair on my head but, as Joerg notes,
SWMBO objects to such a severe treatment

Wow, I had you both pegged as more like Willie Nelson.

Nah, then they'd both be driving a big truck with mud flaps and them big
errialls ;-)

Or at least a Harley like them's guys out here who performed with him at
times:
http://dixonmayfair.com/news/news050407.html

Scary, very scary. I've ridden on a motorcycle once in my life--it was
a Yamaha RD400 (two-stroke) and I was on the back. Problem was, the
other guy was about half my size, and the bike went where *I* leaned,
not where he did. We never even got out of the parking lot.

I've had 13 motorcycle crashes on the street, about half involving
cars, and literally hundreds in the dirt, a few of which involved
trees. My wife is a speech pathologist who has worked on too many guys
who will be goofy or veggies for the rest of their lives, so I sold my
bikes. Besides, the drivers are way too scary these days.

But I still ski.[/QUOTE]

I've dropped my bike, driven it off a cliff (inadvertently - it was an
unknown hill with a sheer drop-off into thorn bushes on the other side),
burned out the clutch, dropped it again, etc., but I've only ever had
one actual "collision" with it: I lost it just enough in a left turn
to sideswipe a parked car. I was able to blame the first drizzle of the
season, but got really paranoid in turns after it.

They tagged the car owner, because it was a "No Parking" zone. ;-)
(they sewed me up and I got 30 days' light duty. ;-) )

Cheers!
Rich

 

[Jim Thompson]

Phil Hobbs wrote:
Jim Thompson wrote:
[snip]
My long beard is gone. But I have adopted the
Bruce Willis / Hollywood look, where 2 to 3 days
is optimum. Actually, for me, this translates
into fluctuating between 0 and 15 days.

Bwahahahahaha! And I thought you had no sense of humor.

We BOTH sure look like Bruce Willis don't we ?

(I use the shortest setting on my beard clippers... probably about
1/8"... I'd do the same to the hair on my head but, as Joerg notes,
SWMBO objects to such a severe treatment

...Jim Thompson
Wow, I had you both pegged as more like Willie Nelson.

Nah, then they'd both be driving a big truck with mud flaps and them big
errialls ;-)

Or at least a Harley like them's guys out here who performed with him at
times:
http://dixonmayfair.com/news/news050407.html

I DO own a pick-em-up truck (though it's a Frontier ;-)

That don't count. Mine's also a "Rice Jeep".

What I meant was this kind:
http://www.toughcountry.com/dodge/pages/21_dodge_jpg.htm

I've driven one of those... it's like driving a luxury car.

...Jim Thompson

 

[Joerg]

On Tue, 30 Oct 2007 13:39:34 -0700, Joerg

Phil Hobbs wrote:
Jim Thompson wrote:
[snip]
My long beard is gone. But I have adopted the
Bruce Willis / Hollywood look, where 2 to 3 days
is optimum. Actually, for me, this translates
into fluctuating between 0 and 15 days.

Bwahahahahaha! And I thought you had no sense of humor.

We BOTH sure look like Bruce Willis don't we ?

(I use the shortest setting on my beard clippers... probably about
1/8"... I'd do the same to the hair on my head but, as Joerg notes,
SWMBO objects to such a severe treatment

...Jim Thompson
Wow, I had you both pegged as more like Willie Nelson.

Nah, then they'd both be driving a big truck with mud flaps and them big
errialls ;-)

Or at least a Harley like them's guys out here who performed with him at
times:
http://dixonmayfair.com/news/news050407.html
I DO own a pick-em-up truck (though it's a Frontier ;-)

That don't count. Mine's also a "Rice Jeep".

What I meant was this kind:
http://www.toughcountry.com/dodge/pages/21_dodge_jpg.htm

I've driven one of those... it's like driving a luxury car.

Sure is. Except that I got 20mpg with an "Executive Edition" Crown
Victoria versus 8mpg with a Chevy Dually.

 

[Robert Latest]

The +-15V is really important for dynamic range--I hate
losing 9-10 dB by using +-5, and losing 15 dB for the privilege of using
+5/0 genuinely stinks.

I really don't get it why they do that. Well of course I know but I still
hate it. Recently I've seen a new +-15V amp marketed as "high voltage" (I
think it was National or Linear, or even AD).

robert

 

[Fred Bartoli]

Le Tue, 30 Oct 2007 15:15:46 -0700, John Larkin a écrit:

I've had 13 motorcycle crashes on the street, about half involving cars,
and literally hundreds in the dirt, a few of which involved trees. My
wife is a speech pathologist who has worked on too many guys who will be
goofy or veggies for the rest of their lives, so I sold my bikes.
Besides, the drivers are way too scary these days.

But I still ski.

I'm doing paragliding (a lot).
The last ski teacher I talked to went nut when I told him:
Skiing? No, thanks. It's far too dangerous because it's way too close to
ground.

Comparing both, stats are not in favor of skiing.

 

[Ecnerwal]

Meanwhile I'm sitting on 20 or so LF455/6/7 which obviously did not
survive the intervening 20 years, so I hope I can find the right paper
book (I have some stashed here, and some elsewhere), as National does
not have the datasheets for those on-line, and I'm not over-fond of the
"pay money for datasheet" people. My op-amp book stops at LF453...

Of course there's also the "do I want to use them at all, if they have
been weeded out of the stream" consideration, but I hate to waste things
(other than storage space, evidently).

 

[Robert Latest]

Meanwhile I'm sitting on 20 or so LF455/6/7 which obviously did not
survive the intervening 20 years

A google search on these part numbers brings up exactly nothing opamp-like,
which I've never experienced even for long-gone components.

My op-amp book stops at LF453...

Yeah, those are well-known.

robert

 

[Phil Hobbs]

Meanwhile I'm sitting on 20 or so LF455/6/7 which obviously did not
survive the intervening 20 years, so I hope I can find the right paper
book (I have some stashed here, and some elsewhere), as National does
not have the datasheets for those on-line, and I'm not over-fond of the
"pay money for datasheet" people. My op-amp book stops at LF453...

Of course there's also the "do I want to use them at all, if they have
been weeded out of the stream" consideration, but I hate to waste things
(other than storage space, evidently).

Those were nice parts. I still have some left too...iirc they're in the
1989 data book. I'll look them up and see if I can post the
datasheet--basically they were the LF3xx series with the current limit
resistor pinned out separately, so you could use higher current at lower
supply voltages.

National did some *weird* stuff in 1988--they came out with about 20 new
*hybrid* designs, like the LH4009 buffer. Of course, those lasted about
2 years and went the way of the dodo. I still have some.

Cheers,

Phil Hobbs

 

[Jure Newsgroups]

Thanks Win,
then, the AC coupling is just for the bootstapped
detector bias voltage. The "video" path is good to DC.

My detector amplifiers are not bootstrapped.

The last design has a diff pair of JFETS cascoded
with a couple of BJTs. An OpAmp completes the forward path.

Thanks , Jure Z.

ah, the JFETs are the dual LSK389 , from Linear Systems,
http://www.linearsystems.com/datasheets/LSK389.pdf

no as cheap as Joerg would like, but a nice dual anyway.

Thanks , Jure Z.

 

[John Larkin]

Le Tue, 30 Oct 2007 15:15:46 -0700, John Larkin a écrit:


I'm doing paragliding (a lot).
The last ski teacher I talked to went nut when I told him:
Skiing? No, thanks. It's far too dangerous because it's way too close to
ground.

Comparing both, stats are not in favor of skiing.

But snow is slippery and (often) soft.

A couple of years ago I was skiing backwards pretty fast and hit a
bump. My tips dug in and I went down on my butt, hard, in
milliseconds. I bruised my butt, which I expected, but there must have
been a shock wave or something, because I had a mean-looking matching
bruise on the opposite side, on my belly. The shock wave apparently
didn't hit any vital organs.

John

 

[Joerg]

ah, the JFETs are the dual LSK389 , from Linear Systems,
http://www.linearsystems.com/datasheets/LSK389.pdf

no as cheap as Joerg would like, but a nice dual anyway.

Thanks , Jure Z.

BTW, that brings up an old friend: What happened to the 2N4417? Is it
still for sale somewhere or did I miss the obituary?