TCA0372 troubles

[George Herold]

On Wednesday, June 5, 2019 at 10:51:17 AM UTC-4, piglet wrote:

On 04/06/2019 15:49, George Herold wrote:
On Tuesday, June 4, 2019 at 10:34:31 AM UTC-4, George Herold wrote:
I'm using my first TCA0372 as a ~1-2 Watt heater drive. Unfortunately
I've blown it up three times... twice by accident and this morning on purpose.
Apparently the TCA can't have it's output shorted to ground.
I_out max is 1.0 A (DC),
https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

So I need either some output protection.. current limit. Or another
opamp that does ~100 mA, or I'll have to do some transistor pass element..
it's dead slow so speed is not important.

thoughts?
George H.

Say, Can I parallel opamps on the output for more current? How well
will they share current?

GH


Paralleling op-amps works fine, see:

http://www.ti.com/lit/an/snoa862/snoa862.pdf

Yeah, paralleling worked fine. I did something like
figure 3, but not a bipolar drive. I do like that it has
some built in current limit when shorted.
One thing I worry about is that all the spec sheets I've read
say I'm only allowed to short one opamp per package to ground.

I'm abusing some opamps now... I'll probably use the opa2192.
It seems a bit of a shame to use such a wonderful opamp as just
a heater drive... but at $3 each they are cheaper than some power
opamp.

George H.

Back in 1980s I used that very successfully with the oft-mocked LM324.

piglet

 

[Don Kuenz, KB7RPU]

piglet <erichpwagner@hotmail.com> wrote:

On 04/06/2019 15:49, George Herold wrote:
On Tuesday, June 4, 2019 at 10:34:31 AM UTC-4, George Herold wrote:
I'm using my first TCA0372 as a ~1-2 Watt heater drive. Unfortunately
I've blown it up three times... twice by accident and this morning on purpose.
Apparently the TCA can't have it's output shorted to ground.
I_out max is 1.0 A (DC),
https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

So I need either some output protection.. current limit. Or another
opamp that does ~100 mA, or I'll have to do some transistor pass element..
it's dead slow so speed is not important.

thoughts?
George H.

Say, Can I parallel opamps on the output for more current? How well
will they share current?

GH


Paralleling op-amps works fine, see:

http://www.ti.com/lit/an/snoa862/snoa862.pdf

Back in 1980s I used that very successfully with the oft-mocked LM324.

LB-44 (Pease) tingled my mind enough to pull down the long forgotten
_Linear Applications Handbook_ from my topmost bookshelf and look
inside, where LB-44 was found in all its original glory. That means
that there's no need to download yet another PDF this time around.
_Operational Amplifiers_ (DostĂĄl) was pulled down a few days ago
after opamp offsets piqued my interest. As expected, some of the ANs &
LBs in the NS Handbook also talk about offsets.
There's an interesting, professionally applied, burnt orange
semi-peeled label on the Handbook's spine. It reads "1980" and it's
intended to cover up a "1982" on a burnt orange background that was
originally printed. Weird.

Thank you, 73,

--
Don Kuenz KB7RPU
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.

 

[George Herold]

On Wednesday, June 5, 2019 at 12:28:20 PM UTC-4, George Herold wrote:

On Wednesday, June 5, 2019 at 11:19:41 AM UTC-4, John Larkin wrote:
On Wed, 5 Jun 2019 07:22:15 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Tuesday, June 4, 2019 at 2:38:46 PM UTC-4, George Herold wrote:
On Tuesday, June 4, 2019 at 1:36:07 PM UTC-4, John Larkin wrote:
On Tue, 4 Jun 2019 09:20:04 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Tuesday, June 4, 2019 at 11:46:49 AM UTC-4, John Larkin wrote:
On Tue, 4 Jun 2019 07:34:25 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

I'm using my first TCA0372 as a ~1-2 Watt heater drive. Unfortunately
I've blown it up three times... twice by accident and this morning on purpose.
Apparently the TCA can't have it's output shorted to ground.
I_out max is 1.0 A (DC),
https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

So I need either some output protection.. current limit. Or another
opamp that does ~100 mA, or I'll have to do some transistor pass element..
it's dead slow so speed is not important.

thoughts?
George H.

The data sheet is sketchy, if not evasive. It claims that the chip has
thermal protections but warns against exceeding 1 amp out. There is
nothing that specs actual current capability or current limit.

Is your heater a resistor? That should limit the opamp output current.
Right, but kids have access to the output and can short it.

What's your supply voltage?
24V.
(Here's a pic of the output.)
https://www.dropbox.com/s/v8teqh5a0jep8qt/tca0372.JPG?dl=0



One alternative to using a big opamp is to use a little one and boost
its output using a 3t voltage regulator, LM317 or LM1117, as a power
booster, essentially a smart, protected emitter follower.

Huh.. 317 as power booster? I've used LM395 for that.. but they are
spendy... How do I do that with an LM317? (and what's the dropout?)


Drive the ADJ pin with your signal from a small opamp. A series
resistor and a zener or something can do your square root.

You'll get the +1.25 volt offset, and the dropout on the data sheet.
You'd have to drive ADJ to -1.25 to get zero out.
Right thanks. Say speaking of the 1.25 V drop, if I added a small R
to the output of the '317 and feed that back to the adj pin I could
have it current limit when shorted... I guess I'd need a diode between
the adj pin and low voltage side of current sense R.

I'll try just the '317 first.

George H.
Well the LM317 was a fail as a power transistor. The output never went
below 1.2 volts even with -5V on the 'base' adjust pin.


Makes no sense. How would it know where ground was, to stay 1.2 above
that?

Was your load heater resistor connected, with ground on its other end?
Yeah, I've already ripped up the test circuit.... but the LM395 worked
perfectly in it's place. I could try again... it would be nice to have a
cheap, thermally protected output drive.

OK I made a mistake, the first time I only had a 1 k ohm load on the LM317
And the output voltage (with zero input voltage) changes with the load.

10 k 4.5 V
1 k 1.3 V
0.5k 0.7V
0.33k 0.5 V.

I used the lm317 as an emitter follower. Collector (in) to V+
Base (adj) to opamp output (with 1 k ohm series R)
and emitter (out) to load and feedback.

George h.

George H.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

On Tuesday, June 4, 2019 at 10:34:31 AM UTC-4, George Herold wrote:

I'm using my first TCA0372 as a ~1-2 Watt heater drive. Unfortunately
I've blown it up three times... twice by accident and this morning on purpose.
Apparently the TCA can't have it's output shorted to ground.
I_out max is 1.0 A (DC),
https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

So I need either some output protection.. current limit. Or another
opamp that does ~100 mA, or I'll have to do some transistor pass element..
it's dead slow so speed is not important.

thoughts?
George H.

I've used it as a buffer or low gain amplifier with the same result. The fix was to put a resistor about 200-ohms in the feedback path to limit the FB slew rate that the input sees. No more explosions!

 

[George Herold]

On Wednesday, June 5, 2019 at 7:23:40 PM UTC-4, alan.ye...@gmail.com wrote:

On Tuesday, June 4, 2019 at 10:34:31 AM UTC-4, George Herold wrote:
I'm using my first TCA0372 as a ~1-2 Watt heater drive. Unfortunately
I've blown it up three times... twice by accident and this morning on purpose.
Apparently the TCA can't have it's output shorted to ground.
I_out max is 1.0 A (DC),
https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

So I need either some output protection.. current limit. Or another
opamp that does ~100 mA, or I'll have to do some transistor pass element..
it's dead slow so speed is not important.

thoughts?
George H.

I've used it as a buffer or low gain amplifier with the same result. The fix was to put a resistor about 200-ohms in the feedback path to limit the FB slew rate that the input sees. No more explosions!

Thanks Alan, I'm paralleling an opa2192. (outputs have
10 ohm resistors to FB, (master/slave) and then a fat diode
to output.) I left it feeding a shorted output overnight..
it was happily oscillating away.

George H.

 

[Phil Hobbs]

On 6/5/19 10:22 AM, George Herold wrote:

On Tuesday, June 4, 2019 at 2:38:46 PM UTC-4, George Herold wrote:
On Tuesday, June 4, 2019 at 1:36:07 PM UTC-4, John Larkin wrote:
On Tue, 4 Jun 2019 09:20:04 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Tuesday, June 4, 2019 at 11:46:49 AM UTC-4, John Larkin wrote:
On Tue, 4 Jun 2019 07:34:25 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

I'm using my first TCA0372 as a ~1-2 Watt heater drive. Unfortunately
I've blown it up three times... twice by accident and this morning on purpose.
Apparently the TCA can't have it's output shorted to ground.
I_out max is 1.0 A (DC),
https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

So I need either some output protection.. current limit. Or another
opamp that does ~100 mA, or I'll have to do some transistor pass element..
it's dead slow so speed is not important.

thoughts?
George H.

The data sheet is sketchy, if not evasive. It claims that the chip has
thermal protections but warns against exceeding 1 amp out. There is
nothing that specs actual current capability or current limit.

Is your heater a resistor? That should limit the opamp output current.
Right, but kids have access to the output and can short it.

What's your supply voltage?
24V.
(Here's a pic of the output.)
https://www.dropbox.com/s/v8teqh5a0jep8qt/tca0372.JPG?dl=0



One alternative to using a big opamp is to use a little one and boost
its output using a 3t voltage regulator, LM317 or LM1117, as a power
booster, essentially a smart, protected emitter follower.

Huh.. 317 as power booster? I've used LM395 for that.. but they are
spendy... How do I do that with an LM317? (and what's the dropout?)


Drive the ADJ pin with your signal from a small opamp. A series
resistor and a zener or something can do your square root.

You'll get the +1.25 volt offset, and the dropout on the data sheet.
You'd have to drive ADJ to -1.25 to get zero out.
Right thanks. Say speaking of the 1.25 V drop, if I added a small R
to the output of the '317 and feed that back to the adj pin I could
have it current limit when shorted... I guess I'd need a diode between
the adj pin and low voltage side of current sense R.

I'll try just the '317 first.

George H.
Well the LM317 was a fail as a power transistor. The output never went
below 1.2 volts even with -5V on the 'base' adjust pin.

The 317 can't sink current any more than an NPN's emitter can. Apart
from its slow speed and weird offset voltage, it's pretty much
equivalent to a power NPN.

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Bob Engelhardt]

On 6/5/2019 10:51 AM, piglet wrote:

Paralleling op-amps works fine, see:

http://www.ti.com/lit/an/snoa862/snoa862.pdf
...

I'm curious about Fig. 3 there: the circuit controls both sides of the
load - why would they do that? I.e., why not just control one side? (I
know, it's a naive question, but I am too.)

 

[George Herold]

On Wednesday, June 5, 2019 at 10:54:54 PM UTC-4, Phil Hobbs wrote:

On 6/5/19 10:22 AM, George Herold wrote:
On Tuesday, June 4, 2019 at 2:38:46 PM UTC-4, George Herold wrote:
On Tuesday, June 4, 2019 at 1:36:07 PM UTC-4, John Larkin wrote:
On Tue, 4 Jun 2019 09:20:04 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Tuesday, June 4, 2019 at 11:46:49 AM UTC-4, John Larkin wrote:
On Tue, 4 Jun 2019 07:34:25 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

I'm using my first TCA0372 as a ~1-2 Watt heater drive. Unfortunately
I've blown it up three times... twice by accident and this morning on purpose.
Apparently the TCA can't have it's output shorted to ground.
I_out max is 1.0 A (DC),
https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

So I need either some output protection.. current limit. Or another
opamp that does ~100 mA, or I'll have to do some transistor pass element..
it's dead slow so speed is not important.

thoughts?
George H.

The data sheet is sketchy, if not evasive. It claims that the chip has
thermal protections but warns against exceeding 1 amp out. There is
nothing that specs actual current capability or current limit.

Is your heater a resistor? That should limit the opamp output current.
Right, but kids have access to the output and can short it.

What's your supply voltage?
24V.
(Here's a pic of the output.)
https://www.dropbox.com/s/v8teqh5a0jep8qt/tca0372.JPG?dl=0



One alternative to using a big opamp is to use a little one and boost
its output using a 3t voltage regulator, LM317 or LM1117, as a power
booster, essentially a smart, protected emitter follower.

Huh.. 317 as power booster? I've used LM395 for that.. but they are
spendy... How do I do that with an LM317? (and what's the dropout?)


Drive the ADJ pin with your signal from a small opamp. A series
resistor and a zener or something can do your square root.

You'll get the +1.25 volt offset, and the dropout on the data sheet.
You'd have to drive ADJ to -1.25 to get zero out.
Right thanks. Say speaking of the 1.25 V drop, if I added a small R
to the output of the '317 and feed that back to the adj pin I could
have it current limit when shorted... I guess I'd need a diode between
the adj pin and low voltage side of current sense R.

I'll try just the '317 first.

George H.
Well the LM317 was a fail as a power transistor. The output never went
below 1.2 volts even with -5V on the 'base' adjust pin.

The 317 can't sink current any more than an NPN's emitter can. Apart
from its slow speed and weird offset voltage, it's pretty much
equivalent to a power NPN.

Yeah, I'm not sure. The LM395 worked as expected... maybe someday I'll
play around more (there must be a spice model for the lm317.)

The dual/parallel opamps worked great, with the advantage that
the max current is 120 mA. So it doesn't stress the power supply...
I'm going to lay that out today.

George H.

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[piglet]

On 06/06/2019 1:37 pm, Bob Engelhardt wrote:

On 6/5/2019 10:51 AM, piglet wrote:
Paralleling op-amps works fine, see:

http://www.ti.com/lit/an/snoa862/snoa862.pdf
...

I'm curious about Fig. 3 there: the circuit controls both sides of the
load - why would they do that?  I.e., why not just control one side?  (I
know, it's a naive question, but I am too.)

Fig. 3 is just an example of extending the technique to drive a floating
load.

piglet

 

[Lasse Langwadt Christense]

torsdag den 6. juni 2019 kl. 18.11.29 UTC+2 skrev Bob Engelhardt:

On 6/6/2019 8:50 AM, piglet wrote:
On 06/06/2019 1:37 pm, Bob Engelhardt wrote:
On 6/5/2019 10:51 AM, piglet wrote:
Paralleling op-amps works fine, see:

http://www.ti.com/lit/an/snoa862/snoa862.pdf
...

I'm curious about Fig. 3 there: the circuit controls both sides of the
load - why would they do that?  I.e., why not just control one side?
(I know, it's a naive question, but I am too.)

Fig. 3 is just an example of extending the technique to drive a floating
load.

piglet


OK, then why does one need to float a load?

double voltage swing, no need for a bipolar supply.

https://en.wikipedia.org/wiki/Bridged_and_paralleled_amplifiers#Bridged_amplifier

 

[Bob Engelhardt]

On 6/6/2019 8:50 AM, piglet wrote:

On 06/06/2019 1:37 pm, Bob Engelhardt wrote:
On 6/5/2019 10:51 AM, piglet wrote:
Paralleling op-amps works fine, see:

http://www.ti.com/lit/an/snoa862/snoa862.pdf
...

I'm curious about Fig. 3 there: the circuit controls both sides of the
load - why would they do that?  I.e., why not just control one side?
(I know, it's a naive question, but I am too.)

Fig. 3 is just an example of extending the technique to drive a floating
load.

piglet

OK, then why does one need to float a load?

 

[George Herold]

On Thursday, June 6, 2019 at 12:11:29 PM UTC-4, Bob Engelhardt wrote:

On 6/6/2019 8:50 AM, piglet wrote:
On 06/06/2019 1:37 pm, Bob Engelhardt wrote:
On 6/5/2019 10:51 AM, piglet wrote:
Paralleling op-amps works fine, see:

http://www.ti.com/lit/an/snoa862/snoa862.pdf
...

I'm curious about Fig. 3 there: the circuit controls both sides of the
load - why would they do that?  I.e., why not just control one side?
(I know, it's a naive question, but I am too.)

Fig. 3 is just an example of extending the technique to drive a floating
load.

piglet


OK, then why does one need to float a load?

I call it a bipolar drive. It's good for things like TEC's. You can
get twice the voltage drive.

George H.

 

[Phil Hobbs]

On 6/5/19 10:22 AM, George Herold wrote:

On Tuesday, June 4, 2019 at 2:38:46 PM UTC-4, George Herold wrote:
On Tuesday, June 4, 2019 at 1:36:07 PM UTC-4, John Larkin wrote:
On Tue, 4 Jun 2019 09:20:04 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Tuesday, June 4, 2019 at 11:46:49 AM UTC-4, John Larkin wrote:
On Tue, 4 Jun 2019 07:34:25 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

I'm using my first TCA0372 as a ~1-2 Watt heater drive. Unfortunately
I've blown it up three times... twice by accident and this morning on purpose.
Apparently the TCA can't have it's output shorted to ground.
I_out max is 1.0 A (DC),
https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

So I need either some output protection.. current limit. Or another
opamp that does ~100 mA, or I'll have to do some transistor pass element..
it's dead slow so speed is not important.

thoughts?
George H.

The data sheet is sketchy, if not evasive. It claims that the chip has
thermal protections but warns against exceeding 1 amp out. There is
nothing that specs actual current capability or current limit.

Is your heater a resistor? That should limit the opamp output current.
Right, but kids have access to the output and can short it.

What's your supply voltage?
24V.
(Here's a pic of the output.)
https://www.dropbox.com/s/v8teqh5a0jep8qt/tca0372.JPG?dl=0



One alternative to using a big opamp is to use a little one and boost
its output using a 3t voltage regulator, LM317 or LM1117, as a power
booster, essentially a smart, protected emitter follower.

Huh.. 317 as power booster? I've used LM395 for that.. but they are
spendy... How do I do that with an LM317? (and what's the dropout?)


Drive the ADJ pin with your signal from a small opamp. A series
resistor and a zener or something can do your square root.

You'll get the +1.25 volt offset, and the dropout on the data sheet.
You'd have to drive ADJ to -1.25 to get zero out.
Right thanks. Say speaking of the 1.25 V drop, if I added a small R
to the output of the '317 and feed that back to the adj pin I could
have it current limit when shorted... I guess I'd need a diode between
the adj pin and low voltage side of current sense R.

I'll try just the '317 first.

George H.
Well the LM317 was a fail as a power transistor. The output never went
below 1.2 volts even with -5V on the 'base' adjust pin.
I plugged in the LM395 and it worked fine. I'm going to try the
dual opamp (master/ slave) thing.

Weird. It works fine for me. Did it blow up?

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[George Herold]

On Thursday, June 6, 2019 at 1:10:28 PM UTC-4, Phil Hobbs wrote:

On 6/5/19 10:22 AM, George Herold wrote:
On Tuesday, June 4, 2019 at 2:38:46 PM UTC-4, George Herold wrote:
On Tuesday, June 4, 2019 at 1:36:07 PM UTC-4, John Larkin wrote:
On Tue, 4 Jun 2019 09:20:04 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Tuesday, June 4, 2019 at 11:46:49 AM UTC-4, John Larkin wrote:
On Tue, 4 Jun 2019 07:34:25 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

I'm using my first TCA0372 as a ~1-2 Watt heater drive. Unfortunately
I've blown it up three times... twice by accident and this morning on purpose.
Apparently the TCA can't have it's output shorted to ground.
I_out max is 1.0 A (DC),
https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

So I need either some output protection.. current limit. Or another
opamp that does ~100 mA, or I'll have to do some transistor pass element..
it's dead slow so speed is not important.

thoughts?
George H.

The data sheet is sketchy, if not evasive. It claims that the chip has
thermal protections but warns against exceeding 1 amp out. There is
nothing that specs actual current capability or current limit.

Is your heater a resistor? That should limit the opamp output current.
Right, but kids have access to the output and can short it.

What's your supply voltage?
24V.
(Here's a pic of the output.)
https://www.dropbox.com/s/v8teqh5a0jep8qt/tca0372.JPG?dl=0



One alternative to using a big opamp is to use a little one and boost
its output using a 3t voltage regulator, LM317 or LM1117, as a power
booster, essentially a smart, protected emitter follower.

Huh.. 317 as power booster? I've used LM395 for that.. but they are
spendy... How do I do that with an LM317? (and what's the dropout?)


Drive the ADJ pin with your signal from a small opamp. A series
resistor and a zener or something can do your square root.

You'll get the +1.25 volt offset, and the dropout on the data sheet.
You'd have to drive ADJ to -1.25 to get zero out.
Right thanks. Say speaking of the 1.25 V drop, if I added a small R
to the output of the '317 and feed that back to the adj pin I could
have it current limit when shorted... I guess I'd need a diode between
the adj pin and low voltage side of current sense R.

I'll try just the '317 first.

George H.
Well the LM317 was a fail as a power transistor. The output never went
below 1.2 volts even with -5V on the 'base' adjust pin.
I plugged in the LM395 and it worked fine. I'm going to try the
dual opamp (master/ slave) thing.

Weird. It works fine for me. Did it blow up?

Huh, maybe? The only naughty thing I did was -5V through
1k ohm into the base/adj. pin. Is that enough to blow it?
(maybe I should have started with my fav 10k*.)

George H.

*I use 1%, 1/4W TH 10k's for bus/ hook-up wire, and often
throw away the 10 k ohm part. This practice increased
once I discovered that the 10k's costs us less than 1" of bus wire...
(we buy a lot of 10k's and not much bus wire.)

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Jasen Betts]

On 2019-06-05, Don Kuenz KB7RPU <g@crcomp.net> wrote:

piglet <erichpwagner@hotmail.com> wrote:
On 04/06/2019 15:49, George Herold wrote:
On Tuesday, June 4, 2019 at 10:34:31 AM UTC-4, George Herold wrote:
I'm using my first TCA0372 as a ~1-2 Watt heater drive. Unfortunately
I've blown it up three times... twice by accident and this morning on purpose.
Apparently the TCA can't have it's output shorted to ground.
I_out max is 1.0 A (DC),
https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

So I need either some output protection.. current limit. Or another
opamp that does ~100 mA, or I'll have to do some transistor pass element..
it's dead slow so speed is not important.

thoughts?
George H.

Say, Can I parallel opamps on the output for more current? How well
will they share current?

GH


Paralleling op-amps works fine, see:

http://www.ti.com/lit/an/snoa862/snoa862.pdf

Back in 1980s I used that very successfully with the oft-mocked LM324.

LB-44 (Pease) tingled my mind enough to pull down the long forgotten
_Linear Applications Handbook_ from my topmost bookshelf and look
inside, where LB-44 was found in all its original glory. That means
that there's no need to download yet another PDF this time around.
_Operational Amplifiers_ (DostĂĄl) was pulled down a few days ago
after opamp offsets piqued my interest. As expected, some of the ANs &
LBs in the NS Handbook also talk about offsets.
There's an interesting, professionally applied, burnt orange
semi-peeled label on the Handbook's spine. It reads "1980" and it's
intended to cover up a "1982" on a burnt orange background that was
originally printed. Weird.

Perhaps someone sent a preview copy of the 82 book to select
individuakls disguised as the 80 book. The page facing the title
page probably has the gory details.

--
When I tried casting out nines I made a hash of it.

 

[Don Kuenz]

Jasen Betts <jasen@xnet.co.nz> wrote:

On 2019-06-05, Don Kuenz KB7RPU <g@crcomp.net> wrote:
piglet <erichpwagner@hotmail.com> wrote:

<snip>

Paralleling op-amps works fine, see:

http://www.ti.com/lit/an/snoa862/snoa862.pdf

Back in 1980s I used that very successfully with the oft-mocked LM324.

LB-44 (Pease) tingled my mind enough to pull down the long forgotten
_Linear Applications Handbook_ from my topmost bookshelf and look
inside, where LB-44 was found in all its original glory. That means
that there's no need to download yet another PDF this time around.
_Operational Amplifiers_ (DostĂĄl) was pulled down a few days ago
after opamp offsets piqued my interest. As expected, some of the ANs &
LBs in the NS Handbook also talk about offsets.
There's an interesting, professionally applied, burnt orange
semi-peeled label on the Handbook's spine. It reads "1980" and it's
intended to cover up a "1982" on a burnt orange background that was
originally printed. Weird.

Perhaps someone sent a preview copy of the 82 book to select
individuakls disguised as the 80 book. The page facing the title
page probably has the gory details.

The closest thing to a title page is the first page inside the cover,
which contains a header that says:

Linear Applications Handbook
----------------------------
National
Semiconductor

The purpose of this handbookd is to provide a fully indexed and
cross-referenced collection of linear ...

There is no copyright data on the inside front cover. Oddly enough the
other side of the first page (the second page) contains Acknowledgments,
and includes R. J. Widlar but excludes Pease. The remaining fourty-one
people listed with Widlar are unknown to me.
The book sort of has the vibe of a tome thrown together to hand out
at trade shows, ergo the professional label and sloppy copyright.

On second glance, there's a tiny:

Š 1982 National Semiconductor Corp.

near the bottom left corner of the rear cover. (It earlier seemed
extremely doubtful that corporate lawyers would ever allow something to
escape the corporate confines without a copyright.)
In the end, we're left with a book printed in 1982, which pretends
that it's from 1980. It seems a corporate fubar one way or the other.

73,

--
Don Kuenz, KB7RPU

 

[Don Kuenz]

Jasen Betts <jasen@xnet.co.nz> wrote:

On 2019-06-05, Don Kuenz KB7RPU <g@crcomp.net> wrote:
piglet <erichpwagner@hotmail.com> wrote:

<snip>

Paralleling op-amps works fine, see:

http://www.ti.com/lit/an/snoa862/snoa862.pdf

Back in 1980s I used that very successfully with the oft-mocked LM324.

LB-44 (Pease) tingled my mind enough to pull down the long forgotten
_Linear Applications Handbook_ from my topmost bookshelf and look
inside, where LB-44 was found in all its original glory. That means
that there's no need to download yet another PDF this time around.
_Operational Amplifiers_ (DostĂĄl) was pulled down a few days ago
after opamp offsets piqued my interest. As expected, some of the ANs &
LBs in the NS Handbook also talk about offsets.
There's an interesting, professionally applied, burnt orange
semi-peeled label on the Handbook's spine. It reads "1980" and it's
intended to cover up a "1982" on a burnt orange background that was
originally printed. Weird.

Perhaps someone sent a preview copy of the 82 book to select
individuakls disguised as the 80 book. The page facing the title
page probably has the gory details.

The closest thing to a title page is the first page inside the cover,
which contains a header that says:

Linear Applications Handbook
----------------------------
National
Semiconductor

The purpose of this handbookd is to provide a fully indexed and
cross-referenced collection of linear ...

There is no copyright data on the inside front cover. Oddly enough the
other side of the first page (the second page) contains Acknowledgments,
and includes R. J. Widlar but excludes Pease. The remaining fourty-one
people listed with Widlar are unknown to me.
The book sort of has the vibe of a tome thrown together to hand out
at trade shows, ergo the professional label and sloppy copyright.

73,

--
Don Kuenz, KB7RPU