Driver to drive?

Jim Thompson · Jan 26, 2012

On Wed, 25 Jan 2012 23:53:45 -0600, Lostgallifreyan
<no-one@nowhere.net> wrote:

Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
news:1ia1i7t48tsitavjukpdub0jn0o1mukk5l@4ax.com:

The data sheet is amongst the worst I've ever seen.

Can you collect the following data:

(1) Unloaded supply current versus total supply voltage

(2) Maximum SINK current capability versus total supply voltage

I got three samples of Intersil CA3140, of various ages, likely from
different sources, each set up as a voltage follower: wire links from Out
back to -In, +in to V- rail. The output was unloaded. 33 readings for each
IC. This data set may well be overkill, but I want quality so I have to give
it. It takes some endurance and patience with my setup to get stable
readings this accurate, so I'll sleep before I try for the sink currents.

Is there any change I must make to that voltage follower circuit I described
just now, for the sink current tests? Also, I assumed I'd have to limit the
current in whatever was on the output to prevent damage to the output, so I
don't understand what is needed to set up that test. (Might if I was less
tired, but please save me from a silly mistake tomorrow, as I have callers
to measure up fencing and cracked glass, plenty of distractions....)

[snip]

The implication from the data sheet is that it's limited to some small
amount... the data sheet says, at 5V, Isinkmax=1mA :-(

Maybe, as a follower, input biased at midpoint, pull up output with a
voltage source (gently

Lostgallifreyan · Jan 26, 2012

Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
news:lar2i7tpd1ladt5dlbdsjar1rir3m0dgku@4ax.com:

Maybe, as a follower, input biased at midpoint, pull up output with a
voltage source (gently and observe current?

Midpoint between negative and positive supply, or between negative and the
same fixed voltage that pulls up the output? (I'll use 5V through a resistor
value of your choosing for the output pullup, so we have known conditions).

Robert Macy · Jan 26, 2012

On Jan 25, 12:18 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:

On Wed, 25 Jan 2012 09:27:46 -0800 (PST), Robert Macy

robert.a.m...@gmail.com> wrote:
On Jan 25, 9:48 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 25 Jan 2012 16:53:17 +1100, "Phil Allison" <phi...@tpg.com.au
wrote:

"John Larkin"
"Phil Allison"

"Tim Williams is so full of shit "

Yes, suffice it to say, even though (dry slug) tantalums tend to
have
ESR
comparable to (higher grade) electrolytics, they are far, far
simpler:

** Their failure modes are many and failures far more common too.

If you keep dV/dT down, they are very reliable.

** Absolute crap.

As fucking usual, Larkin has no idea of what he speaks and does not
give
a shit either.

I've used well over 100,000 tantalum caps in the last 6 years or so.
53,000 of 2.2u 20v alone. The only ones that failed were loaded
backwards or were on power rails that had high dV/dT available.

** So you have NOT seen the general failure rates with all brands of
tants
and across all types of equipment.

You know no-one who has and do not give a shit either.

Fuck off to hell - you rabid, septic psychopath.

I see very low failure rates in the equipmennt I design. I'm sure
there is badly designed gear that blows tantalum caps.

I'm not a repair tech, so I don't deal with a lot of equipment
designed by somebody else.

** SO SHUT THE FUCK UP

- YOU BLOODY IMBECILE !!!!!!!

.... Phil

I think your ESR tester doesn't work very well with low-uF parts.

John

Use your SoundCard and a little fussing and you can get down to
milliohms between the ranges of 1000Hz to 90kHz. Actually, 89kHz, but
can't get to 100kHz.

A little software and your Soundcard 24bit? running at 192kS/s dual
channel

The signal generator+scope thing I posted is simple. No software. And
it gives you the full time-domain current step response, down to
nanoseconds, which contains a lot of information. 90 KHz is slow for a
lot of applications.

John

I prefer the HP network analyzer with built in model value generation,
good to 500MHz - especially if you want an eye opener as to EXACTLY
what a component is doing to you over a large spectrum. I was not
disparaging your approach, only mentioning there are 'alternative'
tools out there, for the monetarily challenged.

Jim Thompson · Jan 26, 2012

On Thu, 26 Jan 2012 09:51:10 -0600, Lostgallifreyan
<no-one@nowhere.net> wrote:

Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
news:lar2i7tpd1ladt5dlbdsjar1rir3m0dgku@4ax.com:

Maybe, as a follower, input biased at midpoint, pull up output with a
voltage source (gently and observe current?

Midpoint between negative and positive supply,

My original thought.

or between negative and the
same fixed voltage that pulls up the output? (I'll use 5V through a resistor
value of your choosing for the output pullup, so we have known conditions).

Lostgallifreyan · Jan 26, 2012

Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
news:88u2i7l7ud01f95vccnquh5c7t167ufvj3@4ax.com:

Maybe easier: Use split supplies, ground input, then use variable
resistor to +. When output lifts from zero, that's the maximum sink
current.

Nice, that fits with a vague idea I had earlier too. I'll set that up later
and get you some results. With two tweaks per sampling it will take longer
but I like the method.

John Larkin · Jan 26, 2012

On Thu, 26 Jan 2012 07:02:33 -0800 (PST), Robert Macy
<robert.a.macy@gmail.com> wrote:

On Jan 25, 12:18 pm, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 25 Jan 2012 09:27:46 -0800 (PST), Robert Macy

robert.a.m...@gmail.com> wrote:
On Jan 25, 9:48 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 25 Jan 2012 16:53:17 +1100, "Phil Allison" <phi...@tpg.com.au
wrote:

"John Larkin"
"Phil Allison"

"Tim Williams is so full of shit "

Yes, suffice it to say, even though (dry slug) tantalums tend to
have
ESR
comparable to (higher grade) electrolytics, they are far, far
simpler:

** Their failure modes are many and failures far more common too.

If you keep dV/dT down, they are very reliable.

** Absolute crap.

As fucking usual, Larkin has no idea of what he speaks and does not
give
a shit either.

I've used well over 100,000 tantalum caps in the last 6 years or so.
53,000 of 2.2u 20v alone. The only ones that failed were loaded
backwards or were on power rails that had high dV/dT available.

** So you have NOT seen the general failure rates with all brands of
tants
and across all types of equipment.

You know no-one who has and do not give a shit either.

Fuck off to hell - you rabid, septic psychopath.

I see very low failure rates in the equipmennt I design. I'm sure
there is badly designed gear that blows tantalum caps.

I'm not a repair tech, so I don't deal with a lot of equipment
designed by somebody else.

** SO SHUT THE FUCK UP

- YOU BLOODY IMBECILE !!!!!!!

.... Phil

I think your ESR tester doesn't work very well with low-uF parts.

John

Use your SoundCard and a little fussing and you can get down to
milliohms between the ranges of 1000Hz to 90kHz. Actually, 89kHz, but
can't get to 100kHz.

A little software and your Soundcard 24bit? running at 192kS/s dual
channel

The signal generator+scope thing I posted is simple. No software. And
it gives you the full time-domain current step response, down to
nanoseconds, which contains a lot of information. 90 KHz is slow for a
lot of applications.

John

I prefer the HP network analyzer with built in model value generation,
good to 500MHz - especially if you want an eye opener as to EXACTLY
what a component is doing to you over a large spectrum. I was not
disparaging your approach, only mentioning there are 'alternative'
tools out there, for the monetarily challenged.

Not having a network analyzer, I can't argue. I hacked the ESR thing
in a couple of minutes from what was in place on my bench. I could
have TDR'd it, too, and got about the same results, but with 20 GHz
effective bandwidth.

I think in the time domain, so the waveform that I posted means a lot
to me. Notice the small cuvature after the initial step, before the
ramp gets linear?

John

Tim Williams · Jan 26, 2012

On Jan 25, 10:36 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:

Have you tried this?

http://tinyurl.com/7xqed3l

Once you sip this, cognac has no purpose any more.

Oooh, fancy. Looks like the Caribbean's answer to Makers Mark

Tim

Lostgallifreyan · Jan 26, 2012

Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
news:88u2i7l7ud01f95vccnquh5c7t167ufvj3@4ax.com:

When output lifts from zero, that's the maximum sink
current.

I think that test might be impossible. I used a single rail as before (my
supply arrangements won't allow a split AND variable supply to test with.)

I grounded the voltage follower input to negative as for the first test. A DC
offset appears on the output, about 3.2mV at 4V supply, rising in nonlinear
slope to about 6.1 mV at 36V supply. Even if this didn't make things
intractably tedious, I found that a Li-ion cell in series with as much as 47K
between output and negative ground causes a few mV added to the offset on
the output, and 83ľA to flow through the output pin, a value that is very
constant from 4V to 36V supply. It suggests that the method fails with no
definable point at which output voltage rises due to loss of current sinking.
Even with the offset there to confuse things, it should have been possible to
see a discontinuous change in the output voltage with respect to current
change around 1 mA if the datasheet is to be beleived. There isn't one, or if
there is, its signal is swamped by noise from offset and whatever else is
going on. I saw the same result with two IC's and didn't try the third.

Lostgallifreyan · Jan 26, 2012

I know that Google isn't all that at times, but beat this for a new low:
No results found for "measuring sink current"

What to do, what to do....?
Surely there IS a way? If not, how and why does anyone specify this for an
op-amp? After today's debacle it will be some time before my head clears
enough to solve this.

Jim Thompson · Jan 26, 2012

On Thu, 26 Jan 2012 15:44:54 -0600, Lostgallifreyan
<no-one@nowhere.net> wrote:

Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
news:88u2i7l7ud01f95vccnquh5c7t167ufvj3@4ax.com:

When output lifts from zero, that's the maximum sink
current.

I think that test might be impossible. I used a single rail as before (my
supply arrangements won't allow a split AND variable supply to test with.)

I grounded the voltage follower input to negative as for the first test. A DC
offset appears on the output, about 3.2mV at 4V supply, rising in nonlinear
slope to about 6.1 mV at 36V supply. Even if this didn't make things
intractably tedious, I found that a Li-ion cell in series with as much as 47K
between output and negative ground causes a few mV added to the offset on
the output, and 83ľA to flow through the output pin, a value that is very
constant from 4V to 36V supply. It suggests that the method fails with no
definable point at which output voltage rises due to loss of current sinking.
Even with the offset there to confuse things, it should have been possible to
see a discontinuous change in the output voltage with respect to current
change around 1 mA if the datasheet is to be beleived. There isn't one, or if
there is, its signal is swamped by noise from offset and whatever else is
going on. I saw the same result with two IC's and didn't try the third.

OK. Single supply. Ground Input. Load Output with resistor to V+.
Lower resistor value until Output is at +1V. Record value of resistor
and of V+. Do that for V+ = 5V, 10V, and 15V. That should be enough
data.

(I have the basic core running to specification. All I need is to add
the sink current.)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice

Lostgallifreyan · Jan 26, 2012

Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
news:0hl3i7d947gvldlhm4sh9kij5d8hsksp39@4ax.com:

OK. Single supply. Ground Input. Load Output with resistor to V+.
Lower resistor value until Output is at +1V. Record value of resistor
and of V+. Do that for V+ = 5V, 10V, and 15V. That should be enough
data.

That won't work either. I set up for 5V supply, found resistors such that a
1K pot (all I have available) in series will find the 1V pullup on output.
What happens is that at just over 200mV it latches up to 2.3V or so! There's
a lot of hysteresis there, I can reduce that to about 1.5V at which point it
suddenly collapses to 147mV.

I remember the datasheet saying that the voltage follower needs at least 3K9
as current limit, so I tried a 4K7 to see if this fixed the problem, but it
doesn't. The ONLY clearly consistent feature of both attempts as this test is
to reveal some hint of nonlinearity. I doubt anything I have will nail it.

I did try a second IC with near-identical results, then set to 10V supply,
and found that the total resistance needed to do it was about 2K less. The
start point of the jump was a similar voltage, and the end point over 8V.

(I have the basic core running to specification. All I need is to add
the sink current.)

I think we're going to have to permanently do without it, or go with the
datasheet nominal declaration. If what you need is a linear(ish) quality,
this amp doesn't seem to have it.

Jim Thompson · Jan 27, 2012

On Thu, 26 Jan 2012 17:37:15 -0600, Lostgallifreyan
<no-one@nowhere.net> wrote:

Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
news:0hl3i7d947gvldlhm4sh9kij5d8hsksp39@4ax.com:

OK. Single supply. Ground Input. Load Output with resistor to V+.
Lower resistor value until Output is at +1V. Record value of resistor
and of V+. Do that for V+ = 5V, 10V, and 15V. That should be enough
data.

That won't work either. I set up for 5V supply, found resistors such that a
1K pot (all I have available) in series will find the 1V pullup on output.
What happens is that at just over 200mV it latches up to 2.3V or so! There's
a lot of hysteresis there, I can reduce that to about 1.5V at which point it
suddenly collapses to 147mV.

I remember the datasheet saying that the voltage follower needs at least 3K9
as current limit, so I tried a 4K7 to see if this fixed the problem, but it
doesn't. The ONLY clearly consistent feature of both attempts as this test is
to reveal some hint of nonlinearity. I doubt anything I have will nail it.

I did try a second IC with near-identical results, then set to 10V supply,
and found that the total resistance needed to do it was about 2K less. The
start point of the jump was a similar voltage, and the end point over 8V.

(I have the basic core running to specification. All I need is to add
the sink current.)

I think we're going to have to permanently do without it, or go with the
datasheet nominal declaration. If what you need is a linear(ish) quality,
this amp doesn't seem to have it.

That dynamic current sink is a crock... as I already opined. If the
schematic is anything resembling that shown in the data sheet, it's
definitely a latch (positive feedback).

Where in the data sheet is the 3K9 requirement?

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice

Lostgallifreyan · Jan 27, 2012

Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
news

7t3i7dcm8as1b1ttsqfst8sbt9tg4pph8@4ax.com:

That dynamic current sink is a crock... as I already opined. If the
schematic is anything resembling that shown in the data sheet, it's
definitely a latch (positive feedback).

Certainly looked like one. If it's of any use, I could maybe do the test
using 100 mV instead of 1V. It may even let me do 200 mV if it latches at
above that on all supply voltages. (Doubtful).

Where in the data sheet is the 3K9 requirement?

Intersil datasheet CA3140, CA3140A, September 1998, File Number 957.4
(Excerpt starts near end of page 7. Whether this is much different from yours
I don't know).

"As mentioned previously, the amplifier inputs can be driven
below the Terminal 4 potential, but a series current limiting
resistor is recommended to limit the maximum input terminal
current to less than 1mA to prevent damage to the input
protection circuitry.
Moreover, some current limiting resistance should be
provided between the inverting input and the output when
the CA3140 is used as a unity gain voltage follower. This
resistance prevents the possibility of extremely large input
signal transients from forcing a signal through the input
protection network and directly driving the internal constant
current source which could result in positive feedback via the
output terminal. A 3.9k resistor is sufficient."

Jim Thompson · Jan 27, 2012

On Thu, 26 Jan 2012 19:25:53 -0600, Lostgallifreyan
<no-one@nowhere.net> wrote:

Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
news7t3i7dcm8as1b1ttsqfst8sbt9tg4pph8@4ax.com:

That dynamic current sink is a crock... as I already opined. If the
schematic is anything resembling that shown in the data sheet, it's
definitely a latch (positive feedback).

Certainly looked like one. If it's of any use, I could maybe do the test
using 100 mV instead of 1V. It may even let me do 200 mV if it latches at
above that on all supply voltages. (Doubtful).

Where in the data sheet is the 3K9 requirement?

Intersil datasheet CA3140, CA3140A, September 1998, File Number 957.4
(Excerpt starts near end of page 7. Whether this is much different from yours
I don't know).

"As mentioned previously, the amplifier inputs can be driven
below the Terminal 4 potential, but a series current limiting
resistor is recommended to limit the maximum input terminal
current to less than 1mA to prevent damage to the input
protection circuitry.
Moreover, some current limiting resistance should be
provided between the inverting input and the output when
the CA3140 is used as a unity gain voltage follower. This
resistance prevents the possibility of extremely large input
signal transients from forcing a signal through the input
protection network and directly driving the internal constant
current source which could result in positive feedback via the
output terminal. A 3.9k resistor is sufficient."

Lostgallifreyan · Jan 27, 2012

Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
news:vh24i79bak8er70nscqnl3d4ip3d6e4sqq@4ax.com:

"As mentioned previously, the amplifier inputs can be driven
below the Terminal 4 potential, but a series current limiting
resistor is recommended to limit the maximum input terminal
current to less than 1mA to prevent damage to the input
protection circuitry.
Moreover, some current limiting resistance should be
provided between the inverting input and the output when
the CA3140 is used as a unity gain voltage follower. This
resistance prevents the possibility of extremely large input
signal transients from forcing a signal through the input
protection network and directly driving the internal constant
current source which could result in positive feedback via the
output terminal. A 3.9k resistor is sufficient."

That's NOT output current limiting.... read carefully.

I realise that, though I don't fully understand it either. I thought what it
was meant to avoid was the result of a fast swing of the output feeding a
transient back to the inverting input, in response to one arriving on the
non-inverting input. Whatever it is exactly, I didn't think the resistor
would fix the latchup problem in that test because that is a result, not a
cause, in this case directly from the pullup. I just tried that resistor
because it was suggested, so NOT trying it seemed like a bad idea. In
practise, I've often used a CA3140 as a voltage follower with a direct link
feedback, no resistor, and never run into trouble. I didn't know about that
3.9K recommendation until a couple of days ago.

Lostgallifreyan · Jan 27, 2012

Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
news:vh24i79bak8er70nscqnl3d4ip3d6e4sqq@4ax.com:

If it's of any use, I could maybe do the test
using 100 mV instead of 1V.

Go, or no go?

Jim Thompson · Jan 27, 2012

On Thu, 26 Jan 2012 20:39:38 -0600, Lostgallifreyan
<no-one@nowhere.net> wrote:

Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
news:vh24i79bak8er70nscqnl3d4ip3d6e4sqq@4ax.com:

If it's of any use, I could maybe do the test
using 100 mV instead of 1V.

Go, or no go?

Put 10K in the feedback just to make sure it isn't latching up via the
input ESD structure.

Use a resistive divider at the input to establish a midpoint input.

Before any loading, verify that output is also midpoint.

Can you get your hands on a decade resistor box?

Start with it set at least 20K

Connect it between output and V+ (thru you ammeter)

Gradually reduce resistance value avoiding massive steps by backing up
to a high setting before down-ranging.

Record current at which output node lifts.

This CA3140 may well be a POS, but your query has stirred my mind to
improve my generalized OpAmp to include:

(1) Output dead-band
(2) Output current limiting, V+ and V- values independently set
(3) Supply currents
(4) Swing limits (including load effects)

All with just 2 simple TANH functions... convergence guaranteed... all
derivatives exist

Jim Thompson · Jan 27, 2012

On Fri, 27 Jan 2012 08:45:34 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

[snip]

This CA3140 may well be a POS, but your query has stirred my mind to
improve my generalized OpAmp to include:

(1) Output dead-band
(2) Output current limiting, V+ and V- values independently set
(3) Supply currents
(4) Swing limits (including load effects)

All with just 2 simple TANH functions... convergence guaranteed... all
derivatives exist

...Jim Thompson

I missed mentioning (5) ROUT... independent values for sourcing and
sinking

John Larkin · Jan 27, 2012

On Thu, 26 Jan 2012 08:42:50 -0800 (PST), Tim Williams
<tmoranwms@gmail.com> wrote:

On Jan 25, 10:36 pm, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
Have you tried this?

http://tinyurl.com/7xqed3l

Once you sip this, cognac has no purpose any more.

Oooh, fancy. Looks like the Caribbean's answer to Makers Mark

Tim

It's actually from Guatemala.

http://en.wikipedia.org/wiki/Ron_Zacapa_Centenario

Try some. Well worth the price.

John

Fred Abse · Jan 27, 2012

On Wed, 25 Jan 2012 15:47:50 -0800, John Larkin wrote:

Does this work?

http://dl.dropbox.com/u/53724080/Circuits/Tant_ESR_Rig.JPG

http://dl.dropbox.com/u/53724080/Circuits/Tant_ESR_Scope.JPG

Yes.

The web site needs work, and it's kind of a nuisance to throw files up
onto. The FTP is really fast and easy, but some people can't see it.

I still vote for ftp.

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

Driver to drive?

Jim Thompson

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