Maintaining a Vbe Multiplier's bias value

On Thu, 11 Feb 2010 10:08:38 -0600, "Tim Williams"

tmoran...@charter.net> wrote:
"Jim Thompson" <To-Email-Use-The-Envelope-I...@My-Web-Site.com> wrote in
messagenews:r358n59g5vkv4brn2vc795lhoineb2jvhd_at_4ax.com...
And a 2.5V "dead-band", but it _is_ precisely known, and temperature
stable.  Interesting thought if you have high enough power supplies.

Bonus: the dead band allows you to use that TL431 "Vbe" mentinoed earlier.

Too bad they're so slow (hardly capable for audio).  Does anyone make "fast"
regulators (without being stupid LDOs)?

Tim

If you drive both adjust pins with the signal input, the 317 output is
Vin+1.25 and the 337 output is Vin-1.25. Connect them to the output
through a couple of resistors, valued to set the idle current. Where's
the deadband?

Or you can take the output from the 317 output pin, with the 337 now
acting like a constant-current sink to the 317.

I like to use LM1117s as power emitter followers, inside the loop of
an opamp. That makes a cheap, well protected power driver, for load
cell excitation and such. I did a bunch of tests to see whether
flailing the adj pin can damage the regulator, and never managed to
break one.

John

"George Herold

So how do you do push pull with tubes, or say with only Jon's npn
transistors?

** There are literally *millions* of push-pull tube amps in use - the vast
majority of tube hifi and guitar amps are push pull designs.

NPN output transistor amps are called "quasi-complementary push pull " -
many millions of them made and sold too.

Use Google to find the schems.

Idiot.

.... Phil

Thanks Phil I'll try google. Why are there still so many tube amps?
You'd think someone could make a solid state amp that sounded
'right'.

On Thu, 11 Feb 2010 11:50:23 -0700, Jim Thompson





To-Email-Use-The-Envelope-I...@My-Web-Site.com> wrote:
On Thu, 11 Feb 2010 10:03:16 -0800, Jon Kirwan
j...@infinitefactors.org> wrote:

On Thu, 11 Feb 2010 09:53:37 -0800, Jon Kirwan
j...@infinitefactors.org> wrote:

snip
In other words, although OnSemi has a realistic model for
their own parts, which is fine for simulating their parts
more accurately -- is there a reason to shop around and
actually _select_ someone else's parts for some application
reason.  And in what cases would you not bother wasting time
shopping around and for what other cases would you decide to
spend the time, because you know enough about how they are
made and what differences that can make to be worth that
effort to test and verify when making a selection?

To further clarify this question, I already know that some
manufacturers provide 2N2222A's with 40V and with 60V max Vce
specifications.  I assume this is a function of differences
in the FAB processes they choose to apply in making their
parts.  That's what I'm talking about... not only for
differences in model parameters but _useful_ differences,
too.

And how do I learn the salient details of various FAB
processes?

Thanks,
Jon

Once upon a time there was JEDEC, and all 2N2222A's had to be the
same in regards to essential specifications.

Okay.  That's gone, then.

But I'd use the OnSemi model, irrespective... the LTspice version lets
too many variables drop back to their default values... might not
matter, but who knows.

                                       ...Jim Thompson

I'd still like to _learn_ about FAB processes, geometries,
mask steps, subtrates (and if any BJTs include a bond to such
things), and differences between them.  For example, I've
heard you talk about processes that include gold as a step
(or more?)  I'd like to know what does what.  I can (and have
attempted) a few 2D spatial integrals aka Hauser's analysis
of crowding on r_b many years ago, and I'm vaguely aware of
the fact that he neglected to account for lateral base
diffusion which happens when the crowding and some local base
widening takes place.  I actually _did_ take measurements of
real Hamamatsu diodes, years ago, and reversed out from the
measurements what the dopant concentrations had to have been
so that I could better model the behavior over a wide range
of temperature operations (Hamamatsu flatly refused to give
me any such information.)  The resulting model I created
_did_ model that photodiode at -40C to 55C better than I'd
expected it to do and much better than the gross models I had
at the time were able.  So at some point, I'd like to study
these things to get a better feel... but I'd like to know who
has what FABs and what the processes are capable of and
produce.

I hope it's not as difficult as pulling dopant numbers out of
Hamamatsu was!  I'm not wanting to know specific recipes or
anything -- just process capabilities.  Hopefully, FAB and
process capabilities and locations are something that is
known about and published.  I can hope.

Jon- Hide quoted text -

- Show quoted text -

On 2/11/2010 10:35 PM, George Herold wrote:
On Feb 11, 1:14 pm, John Larkin

If you drive both adjust pins with the signal input, the 317 output is
Vin+1.25 and the 337 output is Vin-1.25. Connect them to the output
through a couple of resistors, valued to set the idle current. Where's
the deadband?

Or you can take the output from the 317 output pin, with the 337 now
acting like a constant-current sink to the 317.

I like to use LM1117s as power emitter followers, inside the loop of
an opamp. That makes a cheap, well protected power driver, for load
cell excitation and such. I did a bunch of tests to see whether
flailing the adj pin can damage the regulator, and never managed to
break one.

John

Cool! I think I got it... though if I try it in the future and let
the smoke out of something... then I might have questions.

George H.

IIRC the LM395 is basically an LM309 with the voltage reference removed.
Emitter-follower regulators are nearly bulletproof unless you discharge a
cap into the output.

or the reference input. But some power diode antiparallel will take care of

"George Herold

So how do you do push pull with tubes, or say with only Jon's npn
transistors?

** There are literally  *millions* of push-pull tube amps in use -  the vast
majority of tube hifi and guitar amps are push pull designs.

NPN output transistor amps are called "quasi-complementary push pull "  -
many millions of them  made and sold too.

Use Google to find the schems.

Idiot.

....  Phil

On Thu, 11 Feb 2010 19:04:07 -0800 (PST), George Herold
ggherold_at_gmail.com> wrote:

snip

So how do you do push pull with tubes, or say with only Jon's npn
transistors?

George H.

Usually two "NPN" tubes whose plates drive a center-tapped output
transformer.

John

snip

A very comprehensive book, bible lets say is
The Crcuits and Filters Handbook by Chen
don't get fooled by "Handbook", it's the biggest book I got. )
ciao Ban

On Thu, 11 Feb 2010 19:23:04 -0800 (PST), George Herold
ggherold_at_gmail.com> wrote:

On Feb 11, 3:24 am, Jon Kirwan <j...@infinitefactors.org> wrote:
On Wed, 10 Feb 2010 19:55:44 -0800 (PST), George Herold

ggher...@gmail.com> wrote:
I'm perhaps more of a novice than you...

Somehow, I doubt that.  I barely rate "hobbyist."

but I find opamp circuits complicated enough....

Don't sweat it.  While some opamps leave _some_ issues nearly
ignorable, there is always some tough problem at that scale
that makes it non-trivial and interesting to work on, I
imagine.  Each macroscale view has it's own complexity.
Telescoping levels, where the complexity at one stage doesn't
take away from interesting complexity at another level.

(I would say more but I'm keeping in mind your warning about
long-windedness and will now muzzle myself.)

And tend to stick transistors
only on the edges of things.  (Mostly on the output side... on the
input you have to 'know more' than the guys who designed the opamp..
hard to do for a novice.)

I do the same things except that I enjoy math and BJTs give
me an excuse, perhaps.  Maybe that's the only difference.

I guess if I was designing an audio amp I'd figure on an opamp driving
some sort of FET output stage.  The question of how to bias the output
stage is interesting.  And also of how all the NFB works.

Might as well just get a power opamp like the OPA502 and be
done with it.  Give it two rails, feed the input, and just
drive the hell out of a speaker.  Or get two of them and do a
bridge amplifier.  But where is the enjoyment in that?  Or
the learning?  Someone else already did most of the fun stuff
and there's nothing really left to do except some hook up and
heat sinking.  It's not at all satisfying to me, anyway.

An audio amplifier is basically a power opamp.  Using an
opamp to make one feels to me like building a car by first
buying a car without the tires, selecting and installing some
tires, and then saying you designed and built yourself a car.

Jon

Big Grins!

Yeah I applaud your effort, I wait for further posts.

For me, I’m building electronics to either detect something or drive
something that’s detecting something. So the fun is in making good
detectors or drivers.

George H.

Well, I am wanting, eventually, to build something I need.
Something I cannot buy in the market because the need is
unique.

This divides into two parts. Design and build. Since the
item is unique, I can't just go out and buy it. And getting
the features I need cannot just be "hacked" into existing
designs without at least knowing _some_ stuff, first. I
might as well turn the "design" part into a fair learning
experience, as a separate project of its own. Get past that
and when it comes time to build what I want I'll be able to
build on what I learned and add what I need and then do a
modest hobbyist level whack at actually making what I want to
make.

If someone else were to do this for me (hire a designer),
they'd get all the fun of learning on the job and taking my
money with it. They get the money, they get to further their
own education, and I get a tool. One tool. Once. Next
time, I get to pay someone else to learn for me.

It almost feels like paying someone to go do your exercising
for you. No satisfaction and no weight loss. They get all
the _real_ benefits.

Part of the fun isn't the destination itself but it is what
you see and enjoy while getting there, too. You take a plane
when all you need is to "get there" quick, but you drive when
you want to enjoy stops along the way. I used to fly to
Burbank every week for a year and a half. Slept in a hotel
for 3 nights a week, worked day and night in between, flew
home. Barely saw anything but hotel room walls, cubical
walls, a few cement roads, pollution so thick you couldn't
see the Burbank hills from the Lockheed center, and not much
else. The destination was important, of course. Paid the
bills and I enjoyed the work, too. But there is a lot more
to see in the 1000 miles from here to there.

Anyway, I'm driving this time, not flying.

Besides, I'd rather _keep_ the money and _keep_ the education
for myself. That way it pays off, again and again.

Jon

On 2/11/2010 10:35 PM, George Herold wrote:
On Feb 11, 1:14 pm, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Thu, 11 Feb 2010 10:08:38 -0600, "Tim Williams"

tmoran...@charter.net> wrote:
"Jim Thompson"<To-Email-Use-The-Envelope-I...@My-Web-Site.com> wrote in
messagenews:r358n59g5vkv4brn2vc795lhoineb2jvhd_at_4ax.com...
And a 2.5V "dead-band", but it _is_ precisely known, and temperature
stable. Interesting thought if you have high enough power supplies.

Bonus: the dead band allows you to use that TL431 "Vbe" mentinoed earlier.

Too bad they're so slow (hardly capable for audio). Does anyone make "fast"
regulators (without being stupid LDOs)?

Tim

If you drive both adjust pins with the signal input, the 317 output is
Vin+1.25 and the 337 output is Vin-1.25. Connect them to the output
through a couple of resistors, valued to set the idle current. Where's
the deadband?

Or you can take the output from the 317 output pin, with the 337 now
acting like a constant-current sink to the 317.

I like to use LM1117s as power emitter followers, inside the loop of
an opamp. That makes a cheap, well protected power driver, for load
cell excitation and such. I did a bunch of tests to see whether
flailing the adj pin can damage the regulator, and never managed to
break one.

John

Cool! I think I got it... though if I try it in the future and let
the smoke out of something... then I might have questions.

George H.

IIRC the LM395 is basically an LM309 with the voltage reference removed.
Emitter-follower regulators are nearly bulletproof unless you
discharge a cap into the output.

Cheers

Phil Hobbs

"George Herold" <ggherold_at_gmail.com> schrieb im Newsbeitrag
news:f7a4838e-716b-40a8-9b19-7c65cf86dff9_at_o3g2000yqb.googlegroups.com...
On Feb 11, 11:08 pm, "Phil Allison" <phi...@tpg.com.au> wrote:
"George Herold

So how do you do push pull with tubes, or say with only Jon's npn
transistors?

** There are literally *millions* of push-pull tube amps in use - the vast
majority of tube hifi and guitar amps are push pull designs.

NPN output transistor amps are called "quasi-complementary push pull " -
many millions of them made and sold too.

Use Google to find the schems.

Idiot.

.... Phil

Thanks Phil I'll try google. Why are there still so many tube amps?
You'd think someone could make a solid state amp that sounded
'right'.

A lot of transistor amps sound right, but some people prefer to add a bit of
2nd harmonics, or they want to enjoy the gloom.
ciao Ban

On Thu, 11 Feb 2010 19:37:27 -0800, Jon Kirwan
jonk_at_infinitefactors.org> wrote:

On Thu, 11 Feb 2010 19:23:04 -0800 (PST), George Herold
ggherold_at_gmail.com> wrote:

On Feb 11, 3:24 am, Jon Kirwan<j...@infinitefactors.org> wrote:
On Wed, 10 Feb 2010 19:55:44 -0800 (PST), George Herold

ggher...@gmail.com> wrote:
I'm perhaps more of a novice than you...

Somehow, I doubt that. I barely rate "hobbyist."

but I find opamp circuits complicated enough....

Don't sweat it. While some opamps leave _some_ issues nearly
ignorable, there is always some tough problem at that scale
that makes it non-trivial and interesting to work on, I
imagine. Each macroscale view has it's own complexity.
Telescoping levels, where the complexity at one stage doesn't
take away from interesting complexity at another level.

(I would say more but I'm keeping in mind your warning about
long-windedness and will now muzzle myself.)

And tend to stick transistors
only on the edges of things. (Mostly on the output side... on the
input you have to 'know more' than the guys who designed the opamp..
hard to do for a novice.)

I do the same things except that I enjoy math and BJTs give
me an excuse, perhaps. Maybe that's the only difference.

I guess if I was designing an audio amp I'd figure on an opamp driving
some sort of FET output stage. The question of how to bias the output
stage is interesting. And also of how all the NFB works.

Might as well just get a power opamp like the OPA502 and be
done with it. Give it two rails, feed the input, and just
drive the hell out of a speaker. Or get two of them and do a
bridge amplifier. But where is the enjoyment in that? Or
the learning? Someone else already did most of the fun stuff
and there's nothing really left to do except some hook up and
heat sinking. It's not at all satisfying to me, anyway.

An audio amplifier is basically a power opamp. Using an
opamp to make one feels to me like building a car by first
buying a car without the tires, selecting and installing some
tires, and then saying you designed and built yourself a car.

Jon

Big Grins!

Yeah I applaud your effort, I wait for further posts.

For me, I’m building electronics to either detect something or drive
something that’s detecting something. So the fun is in making good
detectors or drivers.

George H.

Well, I am wanting, eventually, to build something I need.
Something I cannot buy in the market because the need is
unique.

This divides into two parts. Design and build. Since the
item is unique, I can't just go out and buy it. And getting
the features I need cannot just be "hacked" into existing
designs without at least knowing _some_ stuff, first. I
might as well turn the "design" part into a fair learning
experience, as a separate project of its own. Get past that
and when it comes time to build what I want I'll be able to
build on what I learned and add what I need and then do a
modest hobbyist level whack at actually making what I want to
make.

If someone else were to do this for me (hire a designer),
they'd get all the fun of learning on the job and taking my
money with it. They get the money, they get to further their
own education, and I get a tool. One tool. Once. Next
time, I get to pay someone else to learn for me.

It almost feels like paying someone to go do your exercising
for you. No satisfaction and no weight loss. They get all
the _real_ benefits.

Part of the fun isn't the destination itself but it is what
you see and enjoy while getting there, too. You take a plane
when all you need is to "get there" quick, but you drive when
you want to enjoy stops along the way. I used to fly to
Burbank every week for a year and a half. Slept in a hotel
for 3 nights a week, worked day and night in between, flew
home. Barely saw anything but hotel room walls, cubical
walls, a few cement roads, pollution so thick you couldn't
see the Burbank hills from the Lockheed center, and not much
else. The destination was important, of course. Paid the
bills and I enjoyed the work, too. But there is a lot more
to see in the 1000 miles from here to there.

Anyway, I'm driving this time, not flying.

Besides, I'd rather _keep_ the money and _keep_ the education
for myself. That way it pays off, again and again.

Jon

The fish/fish rule ?

...Jim Thompson

On Thu, 11 Feb 2010 23:13:24 -0500, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:

On 2/11/2010 10:35 PM, George Herold wrote:
On Feb 11, 1:14 pm, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Thu, 11 Feb 2010 10:08:38 -0600, "Tim Williams"

tmoran...@charter.net> wrote:
"Jim Thompson"<To-Email-Use-The-Envelope-I...@My-Web-Site.com> wrote in
messagenews:r358n59g5vkv4brn2vc795lhoineb2jvhd_at_4ax.com...
And a 2.5V "dead-band", but it _is_ precisely known, and temperature
stable. Interesting thought if you have high enough power supplies.

Bonus: the dead band allows you to use that TL431 "Vbe" mentinoed earlier.

Too bad they're so slow (hardly capable for audio). Does anyone make "fast"
regulators (without being stupid LDOs)?

Tim

If you drive both adjust pins with the signal input, the 317 output is
Vin+1.25 and the 337 output is Vin-1.25. Connect them to the output
through a couple of resistors, valued to set the idle current. Where's
the deadband?

Or you can take the output from the 317 output pin, with the 337 now
acting like a constant-current sink to the 317.

I like to use LM1117s as power emitter followers, inside the loop of
an opamp. That makes a cheap, well protected power driver, for load
cell excitation and such. I did a bunch of tests to see whether
flailing the adj pin can damage the regulator, and never managed to
break one.

John

Cool! I think I got it... though if I try it in the future and let
the smoke out of something... then I might have questions.

George H.

IIRC the LM395 is basically an LM309 with the voltage reference removed.
Emitter-follower regulators are nearly bulletproof unless you
discharge a cap into the output.

Cheers

Phil Hobbs

Close, but no cigar, LM395 = LM317 with some metal rearrangements.

I was thinking 317 but then I decided that the 395 was older than that.

I did this analysis for ICE back in 1980:

http://analog-innovations.com/SED/ICE-LM195-LM117.pdf

Additionally: Amusing myself with the thoughts of complementary-
follower-style power amplifiers made from LM317/LM337 pairs, it fails
because both, internally, are NPN's pass devices, so the LM337 has GBW
and stability issues plus it needs substantial idle load to stay
_vaguely_ stable.

On 2/12/2010 9:52 AM, Jim Thompson wrote:
On Thu, 11 Feb 2010 23:13:24 -0500, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:

On 2/11/2010 10:35 PM, George Herold wrote:
On Feb 11, 1:14 pm, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Thu, 11 Feb 2010 10:08:38 -0600, "Tim Williams"

tmoran...@charter.net> wrote:
"Jim Thompson"<To-Email-Use-The-Envelope-I...@My-Web-Site.com> wrote in
messagenews:r358n59g5vkv4brn2vc795lhoineb2jvhd_at_4ax.com...
And a 2.5V "dead-band", but it _is_ precisely known, and temperature
stable. Interesting thought if you have high enough power supplies.

Bonus: the dead band allows you to use that TL431 "Vbe" mentinoed earlier.

Too bad they're so slow (hardly capable for audio). Does anyone make "fast"
regulators (without being stupid LDOs)?

Tim

If you drive both adjust pins with the signal input, the 317 output is
Vin+1.25 and the 337 output is Vin-1.25. Connect them to the output
through a couple of resistors, valued to set the idle current. Where's
the deadband?

Or you can take the output from the 317 output pin, with the 337 now
acting like a constant-current sink to the 317.

I like to use LM1117s as power emitter followers, inside the loop of
an opamp. That makes a cheap, well protected power driver, for load
cell excitation and such. I did a bunch of tests to see whether
flailing the adj pin can damage the regulator, and never managed to
break one.

John

Cool! I think I got it... though if I try it in the future and let
the smoke out of something... then I might have questions.

George H.

IIRC the LM395 is basically an LM309 with the voltage reference removed.
Emitter-follower regulators are nearly bulletproof unless you
discharge a cap into the output.

Cheers

Phil Hobbs

Close, but no cigar, LM395 = LM317 with some metal rearrangements.

I was thinking 317 but then I decided that the 395 was older than that.
I guess not.

I did this analysis for ICE back in 1980:

http://analog-innovations.com/SED/ICE-LM195-LM117.pdf

Additionally: Amusing myself with the thoughts of complementary-
follower-style power amplifiers made from LM317/LM337 pairs, it fails
because both, internally, are NPN's pass devices, so the LM337 has GBW
and stability issues plus it needs substantial idle load to stay
_vaguely_ stable.

Non-LDO three-terminal regulators are so trouble-free that it's easy to
confuse them with Newton's laws. ;)

Cheers

Phil Hobbs

Build a man a fire, you keep him warm for a night. Set a man afire, you
keep him warm for the rest of his life. ;)

Cheers

Phil Hobbs

On Thu, 11 Feb 2010 19:04:07 -0800 (PST), George Herold





ggher...@gmail.com> wrote:
On Feb 10, 10:34 pm, "Phil Allison" <phi...@tpg.com.au> wrote:
"George Herold"
"Phil Allison"

** Push-pull class A is the MOST COMMON method use in tube and transistor
audio power amplifiers.

With transistor amps, it is only necessary to set to standing bias current
to a high value like an amp or two.

You can, but it stops being class A for large signal swings or low load
impedances.

** No need for either thing to happen.

One picks the load to suit the amplifier and the peak ( class A) current
is
double the bias setting current.

Eg:

With a bias of 2 amps, peak load current is 4amps which allows +/-32 volts
into 8 ohms.

Class A power is then 64 watts rms.

The DC rails need to be about +/- 35 volts and the supply current a steady
2
amps.

Do you just use a current source as bias as in the Amps from Pass labs?

** No - doing that is utterly STUPID.

The only difference between a class A and class B push-pull amp IS the
bias setting.

One just turns the bias trim pot to get the desired standing current or with
tubes adjust the grid bias to get the same result.

Tubes can't do push-pull because "it's hard to get positrons from the
filament" to parapharse what I read.

** How pathetic.

.... Phil- Hide quoted text -

- Show quoted text -

Excellent,  Thanks Phil.  Crank up the bias.

I think almost everything I build runs class A.  I set a DC bias and
then modulate on top of it.  I run an opamp into a pass element, apply
feedback and then make the load 'look' as resistive as possible.
(Then cross your fingers and see if that works.)

So how do you do push pull with tubes, or say with only Jon's npn
transistors?

George H.

Usually two "NPN" tubes whose plates drive a center-tapped output
transformer.

John- Hide quoted text -

- Show quoted text -