TCA0372 shortage?...

[bitrex]

On 7/23/2020 8:55 PM, Lasse Langwadt Christensen wrote:

fredag den 24. juli 2020 kl. 02.32.21 UTC+2 skrev bitrex:
On 7/23/2020 7:24 PM, Phil Hobbs wrote:
On 2020-07-23 19:01, Lasse Langwadt Christensen wrote:
torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2 months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail, and my
go-to floating ground generator is getting scarce.   razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf


Awesome, thanks!  It has the same pinout, and for lower supply voltages
it might well be interchangeable.  I\'ll get some and see.

Cheers

Phil Hobbs


Incidentally it\'s cool how the latest revision of the TCA0372 datasheet
was like literally yesterday and it seems no one has noticed the output
stage as drawn doesn\'t make sense...

https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

I did notice the output on the block diagram made no sense the way
it is drawn, I just assumed some drew an arrow wrong on a transistor
and no one cared

it seems it been that way at least back to the Motorola data sheet I
found dated 1996

Even if they drew the upper stage as a regular Darlington it\'s probably
not a very good representation of the output stage, no ballast resistors
in the emitters and three diode drops but they describe \"zero-deadband
crossover distortion.\" Is the slew-rate symmetric?

There may be some sliding-bias thing going on they don\'t want to
elaborate on.

The ST part uses a current mirror arrangement as the upper driver which
might explain the lower supply rating and offset voltage spec
discrepancy if it exists.

 

[bitrex]

On 7/23/2020 8:55 PM, Lasse Langwadt Christensen wrote:

fredag den 24. juli 2020 kl. 02.32.21 UTC+2 skrev bitrex:
On 7/23/2020 7:24 PM, Phil Hobbs wrote:
On 2020-07-23 19:01, Lasse Langwadt Christensen wrote:
torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2 months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail, and my
go-to floating ground generator is getting scarce.   razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf


Awesome, thanks!  It has the same pinout, and for lower supply voltages
it might well be interchangeable.  I\'ll get some and see.

Cheers

Phil Hobbs


Incidentally it\'s cool how the latest revision of the TCA0372 datasheet
was like literally yesterday and it seems no one has noticed the output
stage as drawn doesn\'t make sense...

https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

I did notice the output on the block diagram made no sense the way
it is drawn, I just assumed some drew an arrow wrong on a transistor
and no one cared

it seems it been that way at least back to the Motorola data sheet I
found dated 1996

Even if they drew the upper stage as a regular Darlington it\'s probably
not a very good representation of the output stage, no ballast resistors
in the emitters and three diode drops but they describe \"zero-deadband
crossover distortion.\" Is the slew-rate symmetric?

There may be some sliding-bias thing going on they don\'t want to
elaborate on.

The ST part uses a current mirror arrangement as the upper driver which
might explain the lower supply rating and offset voltage spec
discrepancy if it exists.

 

[Phil Hobbs]

On 2020-07-23 20:28, Lasse Langwadt Christensen wrote:

fredag den 24. juli 2020 kl. 02.14.39 UTC+2 skrev bitrex:
On 7/23/2020 7:47 PM, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 01.12.21 UTC+2 skrev bitrex:
On 7/23/2020 7:01 PM, Lasse Langwadt Christensen wrote:
torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2 months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail, and my
go-to floating ground generator is getting scarce. razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf


Looks good but they seem a bit un-confident about the offset voltage
spec...???? it\'s usually somewhere in there

page5: input offset voltage -/+10mV ?


Right. The TCA0372 lists 1mV typ and 15 mV max, when there\'s a wide
spread there I get the impression that the 15mV parts are the real
outlier and don\'t show up much in practice. You could use them for DC
application and expect better and QC out a few boards that got a real
bad one.

When it\'s just -/+10 mV with no typ I get the impression that it\'s all
over the place from device to device, so might not be the best choice of
part for a DC-coupled application with gain.

But interpreting datasheets can be mysterious, I\'d guess the TCA would
not be so popular if it were giving offsets at the far end routinely though.

but max might happen, less than 10mV is better than usually 1mV
occupationally 15mV, you have to design for it unless you want to
start sorting

Beasts like that are (IME) used for things like driving servomotors or
making floating ground/supply rails (my usual application). The motors
are inside some outer FB loop, and nobody cares about a 15-mV offset on
a supply rail.

For the occasional precision application, wrap a chopamp feedback loop
round it.

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

 

[Phil Hobbs]

On 2020-07-23 20:28, Lasse Langwadt Christensen wrote:

fredag den 24. juli 2020 kl. 02.14.39 UTC+2 skrev bitrex:
On 7/23/2020 7:47 PM, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 01.12.21 UTC+2 skrev bitrex:
On 7/23/2020 7:01 PM, Lasse Langwadt Christensen wrote:
torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2 months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail, and my
go-to floating ground generator is getting scarce. razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf


Looks good but they seem a bit un-confident about the offset voltage
spec...???? it\'s usually somewhere in there

page5: input offset voltage -/+10mV ?


Right. The TCA0372 lists 1mV typ and 15 mV max, when there\'s a wide
spread there I get the impression that the 15mV parts are the real
outlier and don\'t show up much in practice. You could use them for DC
application and expect better and QC out a few boards that got a real
bad one.

When it\'s just -/+10 mV with no typ I get the impression that it\'s all
over the place from device to device, so might not be the best choice of
part for a DC-coupled application with gain.

But interpreting datasheets can be mysterious, I\'d guess the TCA would
not be so popular if it were giving offsets at the far end routinely though.

but max might happen, less than 10mV is better than usually 1mV
occupationally 15mV, you have to design for it unless you want to
start sorting

Beasts like that are (IME) used for things like driving servomotors or
making floating ground/supply rails (my usual application). The motors
are inside some outer FB loop, and nobody cares about a 15-mV offset on
a supply rail.

For the occasional precision application, wrap a chopamp feedback loop
round it.

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

 

[Lasse Langwadt Christensen]

fredag den 24. juli 2020 kl. 03.22.53 UTC+2 skrev bitrex:

On 7/23/2020 8:55 PM, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 02.32.21 UTC+2 skrev bitrex:
On 7/23/2020 7:24 PM, Phil Hobbs wrote:
On 2020-07-23 19:01, Lasse Langwadt Christensen wrote:
torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2 months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail, and my
go-to floating ground generator is getting scarce.   razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf


Awesome, thanks!  It has the same pinout, and for lower supply voltages
it might well be interchangeable.  I\'ll get some and see.

Cheers

Phil Hobbs


Incidentally it\'s cool how the latest revision of the TCA0372 datasheet
was like literally yesterday and it seems no one has noticed the output
stage as drawn doesn\'t make sense...

https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

I did notice the output on the block diagram made no sense the way
it is drawn, I just assumed some drew an arrow wrong on a transistor
and no one cared

it seems it been that way at least back to the Motorola data sheet I
found dated 1996


Even if they drew the upper stage as a regular Darlington it\'s probably
not a very good representation of the output stage, no ballast resistors
in the emitters and three diode drops but they describe \"zero-deadband
crossover distortion.\" Is the slew-rate symmetric?

doesn\'t look symmetric on fig7

three diodes should match an darlington and compound pair no?

 

[Lasse Langwadt Christensen]

fredag den 24. juli 2020 kl. 03.22.53 UTC+2 skrev bitrex:

On 7/23/2020 8:55 PM, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 02.32.21 UTC+2 skrev bitrex:
On 7/23/2020 7:24 PM, Phil Hobbs wrote:
On 2020-07-23 19:01, Lasse Langwadt Christensen wrote:
torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2 months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail, and my
go-to floating ground generator is getting scarce.   razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf


Awesome, thanks!  It has the same pinout, and for lower supply voltages
it might well be interchangeable.  I\'ll get some and see.

Cheers

Phil Hobbs


Incidentally it\'s cool how the latest revision of the TCA0372 datasheet
was like literally yesterday and it seems no one has noticed the output
stage as drawn doesn\'t make sense...

https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

I did notice the output on the block diagram made no sense the way
it is drawn, I just assumed some drew an arrow wrong on a transistor
and no one cared

it seems it been that way at least back to the Motorola data sheet I
found dated 1996


Even if they drew the upper stage as a regular Darlington it\'s probably
not a very good representation of the output stage, no ballast resistors
in the emitters and three diode drops but they describe \"zero-deadband
crossover distortion.\" Is the slew-rate symmetric?

doesn\'t look symmetric on fig7

three diodes should match an darlington and compound pair no?

 

[bitrex]

On 7/23/2020 9:34 PM, Lasse Langwadt Christensen wrote:

fredag den 24. juli 2020 kl. 03.22.53 UTC+2 skrev bitrex:
On 7/23/2020 8:55 PM, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 02.32.21 UTC+2 skrev bitrex:
On 7/23/2020 7:24 PM, Phil Hobbs wrote:
On 2020-07-23 19:01, Lasse Langwadt Christensen wrote:
torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2 months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail, and my
go-to floating ground generator is getting scarce.   razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf


Awesome, thanks!  It has the same pinout, and for lower supply voltages
it might well be interchangeable.  I\'ll get some and see.

Cheers

Phil Hobbs


Incidentally it\'s cool how the latest revision of the TCA0372 datasheet
was like literally yesterday and it seems no one has noticed the output
stage as drawn doesn\'t make sense...

https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

I did notice the output on the block diagram made no sense the way
it is drawn, I just assumed some drew an arrow wrong on a transistor
and no one cared

it seems it been that way at least back to the Motorola data sheet I
found dated 1996


Even if they drew the upper stage as a regular Darlington it\'s probably
not a very good representation of the output stage, no ballast resistors
in the emitters and three diode drops but they describe \"zero-deadband
crossover distortion.\" Is the slew-rate symmetric?

doesn\'t look symmetric on fig7

three diodes should match an darlington and compound pair no?

Yeah but that puts it in class B and there will be no crossover
distortion if all the transistor junction drops are always matched to
those of the diodes, how are the drops matched when the output devices
heat up. maybe the diodes and transistor junctions are matched enough
because they\'re on the same die and well-coupled enough to the output
devices?

Don\'t know enough about doing power amps on an IC to know how they
accomplish this.

 

[bitrex]

On 7/23/2020 9:34 PM, Lasse Langwadt Christensen wrote:

fredag den 24. juli 2020 kl. 03.22.53 UTC+2 skrev bitrex:
On 7/23/2020 8:55 PM, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 02.32.21 UTC+2 skrev bitrex:
On 7/23/2020 7:24 PM, Phil Hobbs wrote:
On 2020-07-23 19:01, Lasse Langwadt Christensen wrote:
torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2 months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail, and my
go-to floating ground generator is getting scarce.   razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf


Awesome, thanks!  It has the same pinout, and for lower supply voltages
it might well be interchangeable.  I\'ll get some and see.

Cheers

Phil Hobbs


Incidentally it\'s cool how the latest revision of the TCA0372 datasheet
was like literally yesterday and it seems no one has noticed the output
stage as drawn doesn\'t make sense...

https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

I did notice the output on the block diagram made no sense the way
it is drawn, I just assumed some drew an arrow wrong on a transistor
and no one cared

it seems it been that way at least back to the Motorola data sheet I
found dated 1996


Even if they drew the upper stage as a regular Darlington it\'s probably
not a very good representation of the output stage, no ballast resistors
in the emitters and three diode drops but they describe \"zero-deadband
crossover distortion.\" Is the slew-rate symmetric?

doesn\'t look symmetric on fig7

three diodes should match an darlington and compound pair no?

Yeah but that puts it in class B and there will be no crossover
distortion if all the transistor junction drops are always matched to
those of the diodes, how are the drops matched when the output devices
heat up. maybe the diodes and transistor junctions are matched enough
because they\'re on the same die and well-coupled enough to the output
devices?

Don\'t know enough about doing power amps on an IC to know how they
accomplish this.

 

[Phil Hobbs]

On 2020-07-23 21:34, Lasse Langwadt Christensen wrote:

fredag den 24. juli 2020 kl. 03.22.53 UTC+2 skrev bitrex:
On 7/23/2020 8:55 PM, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 02.32.21 UTC+2 skrev bitrex:
On 7/23/2020 7:24 PM, Phil Hobbs wrote:
On 2020-07-23 19:01, Lasse Langwadt Christensen wrote:
torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2 months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail, and my
go-to floating ground generator is getting scarce.   razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf


Awesome, thanks!  It has the same pinout, and for lower supply voltages
it might well be interchangeable.  I\'ll get some and see.

Cheers

Phil Hobbs


Incidentally it\'s cool how the latest revision of the TCA0372 datasheet
was like literally yesterday and it seems no one has noticed the output
stage as drawn doesn\'t make sense...

https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

I did notice the output on the block diagram made no sense the way
it is drawn, I just assumed some drew an arrow wrong on a transistor
and no one cared

it seems it been that way at least back to the Motorola data sheet I
found dated 1996


Even if they drew the upper stage as a regular Darlington it\'s probably
not a very good representation of the output stage, no ballast resistors
in the emitters and three diode drops but they describe \"zero-deadband
crossover distortion.\" Is the slew-rate symmetric?

doesn\'t look symmetric on fig7

three diodes should match an darlington and compound pair no?

The dual-Sziklai totem pole clearly wouldn\'t work as drawn, but it does
suggest the actual performance of the TCA0372--it pulls closer to the
positive rail than your old-school Darlington op amp output. (The lower
limit is much more Darlington-ish.)

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

 

[Phil Hobbs]

On 2020-07-23 21:34, Lasse Langwadt Christensen wrote:

fredag den 24. juli 2020 kl. 03.22.53 UTC+2 skrev bitrex:
On 7/23/2020 8:55 PM, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 02.32.21 UTC+2 skrev bitrex:
On 7/23/2020 7:24 PM, Phil Hobbs wrote:
On 2020-07-23 19:01, Lasse Langwadt Christensen wrote:
torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2 months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail, and my
go-to floating ground generator is getting scarce.   razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf


Awesome, thanks!  It has the same pinout, and for lower supply voltages
it might well be interchangeable.  I\'ll get some and see.

Cheers

Phil Hobbs


Incidentally it\'s cool how the latest revision of the TCA0372 datasheet
was like literally yesterday and it seems no one has noticed the output
stage as drawn doesn\'t make sense...

https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

I did notice the output on the block diagram made no sense the way
it is drawn, I just assumed some drew an arrow wrong on a transistor
and no one cared

it seems it been that way at least back to the Motorola data sheet I
found dated 1996


Even if they drew the upper stage as a regular Darlington it\'s probably
not a very good representation of the output stage, no ballast resistors
in the emitters and three diode drops but they describe \"zero-deadband
crossover distortion.\" Is the slew-rate symmetric?

doesn\'t look symmetric on fig7

three diodes should match an darlington and compound pair no?

The dual-Sziklai totem pole clearly wouldn\'t work as drawn, but it does
suggest the actual performance of the TCA0372--it pulls closer to the
positive rail than your old-school Darlington op amp output. (The lower
limit is much more Darlington-ish.)

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

 

[bitrex]

On 7/23/2020 9:45 PM, bitrex wrote:

On 7/23/2020 9:34 PM, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 03.22.53 UTC+2 skrev bitrex:
On 7/23/2020 8:55 PM, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 02.32.21 UTC+2 skrev bitrex:
On 7/23/2020 7:24 PM, Phil Hobbs wrote:
On 2020-07-23 19:01, Lasse Langwadt Christensen wrote:
torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total
distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2
months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail,
and my
go-to floating ground generator is getting scarce.
razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf


Awesome, thanks!  It has the same pinout, and for lower supply
voltages
it might well be interchangeable.  I\'ll get some and see.

Cheers

Phil Hobbs


Incidentally it\'s cool how the latest revision of the TCA0372
datasheet
was like literally yesterday and it seems no one has noticed the
output
stage as drawn doesn\'t make sense...

https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

I did notice the output on the block diagram made no sense the way
it is drawn, I just assumed some drew an arrow wrong on a transistor
and no one cared

it seems it been that way at least back to the Motorola data sheet I
found dated 1996


Even if they drew the upper stage as a regular Darlington it\'s probably
not a very good representation of the output stage, no ballast resistors
in the emitters and three diode drops but they describe \"zero-deadband
crossover distortion.\" Is the slew-rate symmetric?

doesn\'t look symmetric on fig7

three diodes should match an darlington and compound pair no?



Yeah but that puts it in class B and there will be no crossover
distortion if all the transistor junction drops are always matched to
those of the diodes, how are the drops matched when the output devices
heat up. maybe the diodes and transistor junctions are matched enough
because they\'re on the same die and well-coupled enough to the output
devices?

Don\'t know enough about doing power amps on an IC to know how they
accomplish this.

negative feedback can improve crossover distortion but can\'t eliminate
it and it\'ll get worse as frequency increases and open loop gain drops.
The blurb seem to imply it has zero (or close enough) crossover
distortion, everywhere...

 

[bitrex]

On 7/23/2020 9:45 PM, bitrex wrote:

On 7/23/2020 9:34 PM, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 03.22.53 UTC+2 skrev bitrex:
On 7/23/2020 8:55 PM, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 02.32.21 UTC+2 skrev bitrex:
On 7/23/2020 7:24 PM, Phil Hobbs wrote:
On 2020-07-23 19:01, Lasse Langwadt Christensen wrote:
torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total
distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2
months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail,
and my
go-to floating ground generator is getting scarce.
razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf


Awesome, thanks!  It has the same pinout, and for lower supply
voltages
it might well be interchangeable.  I\'ll get some and see.

Cheers

Phil Hobbs


Incidentally it\'s cool how the latest revision of the TCA0372
datasheet
was like literally yesterday and it seems no one has noticed the
output
stage as drawn doesn\'t make sense...

https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

I did notice the output on the block diagram made no sense the way
it is drawn, I just assumed some drew an arrow wrong on a transistor
and no one cared

it seems it been that way at least back to the Motorola data sheet I
found dated 1996


Even if they drew the upper stage as a regular Darlington it\'s probably
not a very good representation of the output stage, no ballast resistors
in the emitters and three diode drops but they describe \"zero-deadband
crossover distortion.\" Is the slew-rate symmetric?

doesn\'t look symmetric on fig7

three diodes should match an darlington and compound pair no?



Yeah but that puts it in class B and there will be no crossover
distortion if all the transistor junction drops are always matched to
those of the diodes, how are the drops matched when the output devices
heat up. maybe the diodes and transistor junctions are matched enough
because they\'re on the same die and well-coupled enough to the output
devices?

Don\'t know enough about doing power amps on an IC to know how they
accomplish this.

negative feedback can improve crossover distortion but can\'t eliminate
it and it\'ll get worse as frequency increases and open loop gain drops.
The blurb seem to imply it has zero (or close enough) crossover
distortion, everywhere...

 

[bitrex]

On 7/23/2020 9:47 PM, Phil Hobbs wrote:

On 2020-07-23 21:34, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 03.22.53 UTC+2 skrev bitrex:
On 7/23/2020 8:55 PM, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 02.32.21 UTC+2 skrev bitrex:
On 7/23/2020 7:24 PM, Phil Hobbs wrote:
On 2020-07-23 19:01, Lasse Langwadt Christensen wrote:
torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total
distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2
months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail,
and my
go-to floating ground generator is getting scarce.
razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf


Awesome, thanks!  It has the same pinout, and for lower supply
voltages
it might well be interchangeable.  I\'ll get some and see.

Cheers

Phil Hobbs


Incidentally it\'s cool how the latest revision of the TCA0372
datasheet
was like literally yesterday and it seems no one has noticed the
output
stage as drawn doesn\'t make sense...

https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

I did notice the output on the block diagram made no sense the way
it is drawn, I just assumed some drew an arrow wrong on a transistor
and no one cared

it seems it been that way at least back to the Motorola data sheet I
found dated 1996


Even if they drew the upper stage as a regular Darlington it\'s probably
not a very good representation of the output stage, no ballast resistors
in the emitters and three diode drops but they describe \"zero-deadband
crossover distortion.\" Is the slew-rate symmetric?

doesn\'t look symmetric on fig7

three diodes should match an darlington and compound pair no?

The dual-Sziklai totem pole clearly wouldn\'t work as drawn, but it does
suggest the actual performance of the TCA0372--it pulls closer to the
positive rail than your old-school Darlington op amp output.  (The lower
limit is much more Darlington-ish.)

Cheers

Phil Hobbs

it may actually be more like the ST part with the current mirror inside
and the output stage as drawn on the ON part is just (for whatever
reason) sanctioned BS!

 

[bitrex]

On 7/23/2020 9:47 PM, Phil Hobbs wrote:

On 2020-07-23 21:34, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 03.22.53 UTC+2 skrev bitrex:
On 7/23/2020 8:55 PM, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 02.32.21 UTC+2 skrev bitrex:
On 7/23/2020 7:24 PM, Phil Hobbs wrote:
On 2020-07-23 19:01, Lasse Langwadt Christensen wrote:
torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total
distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2
months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail,
and my
go-to floating ground generator is getting scarce.
razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf


Awesome, thanks!  It has the same pinout, and for lower supply
voltages
it might well be interchangeable.  I\'ll get some and see.

Cheers

Phil Hobbs


Incidentally it\'s cool how the latest revision of the TCA0372
datasheet
was like literally yesterday and it seems no one has noticed the
output
stage as drawn doesn\'t make sense...

https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

I did notice the output on the block diagram made no sense the way
it is drawn, I just assumed some drew an arrow wrong on a transistor
and no one cared

it seems it been that way at least back to the Motorola data sheet I
found dated 1996


Even if they drew the upper stage as a regular Darlington it\'s probably
not a very good representation of the output stage, no ballast resistors
in the emitters and three diode drops but they describe \"zero-deadband
crossover distortion.\" Is the slew-rate symmetric?

doesn\'t look symmetric on fig7

three diodes should match an darlington and compound pair no?

The dual-Sziklai totem pole clearly wouldn\'t work as drawn, but it does
suggest the actual performance of the TCA0372--it pulls closer to the
positive rail than your old-school Darlington op amp output.  (The lower
limit is much more Darlington-ish.)

Cheers

Phil Hobbs

it may actually be more like the ST part with the current mirror inside
and the output stage as drawn on the ON part is just (for whatever
reason) sanctioned BS!

 

[bitrex]

On 7/23/2020 8:55 PM, Lasse Langwadt Christensen wrote:

fredag den 24. juli 2020 kl. 02.32.21 UTC+2 skrev bitrex:
On 7/23/2020 7:24 PM, Phil Hobbs wrote:
On 2020-07-23 19:01, Lasse Langwadt Christensen wrote:
torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2 months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail, and my
go-to floating ground generator is getting scarce.   razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf


Awesome, thanks!  It has the same pinout, and for lower supply voltages
it might well be interchangeable.  I\'ll get some and see.

Cheers

Phil Hobbs


Incidentally it\'s cool how the latest revision of the TCA0372 datasheet
was like literally yesterday and it seems no one has noticed the output
stage as drawn doesn\'t make sense...

https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

I did notice the output on the block diagram made no sense the way
it is drawn, I just assumed some drew an arrow wrong on a transistor
and no one cared

it seems it been that way at least back to the Motorola data sheet I
found dated 1996

Even if they drew the upper stage as a regular Darlington it\'s probably
not a very good representation of the output stage, no ballast resistors
in the emitters and three diode drops but they describe \"zero-deadband
crossover distortion.\" Is the slew-rate symmetric?

There may be some sliding-bias thing going on they don\'t want to
elaborate on.

The ST part uses a current mirror arrangement as the upper driver which
might explain the lower supply rating and offset voltage spec
discrepancy if it exists.

 

[server]

On Thu, 23 Jul 2020 16:01:43 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2 months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail, and my
go-to floating ground generator is getting scarce. razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf

Good grief, a drop-in replacement! Almost.

The voltage rating is interesting. 50 volts for 50 milliseconds.

Other strange specs are the single negative supply (0 volts) and the
noise (10 uV).

Good to know about.




--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[server]

On Thu, 23 Jul 2020 16:01:43 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2 months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail, and my
go-to floating ground generator is getting scarce. razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf

Good grief, a drop-in replacement! Almost.

The voltage rating is interesting. 50 volts for 50 milliseconds.

Other strange specs are the single negative supply (0 volts) and the
noise (10 uV).

Good to know about.




--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[server]

On Thu, 23 Jul 2020 16:01:43 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2 months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail, and my
go-to floating ground generator is getting scarce. razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf

Good grief, a drop-in replacement! Almost.

The voltage rating is interesting. 50 volts for 50 milliseconds.

Other strange specs are the single negative supply (0 volts) and the
noise (10 uV).

Good to know about.




--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Lasse Langwadt Christensen]

fredag den 24. juli 2020 kl. 03.48.09 UTC+2 skrev Phil Hobbs:

On 2020-07-23 21:34, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 03.22.53 UTC+2 skrev bitrex:
On 7/23/2020 8:55 PM, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 02.32.21 UTC+2 skrev bitrex:
On 7/23/2020 7:24 PM, Phil Hobbs wrote:
On 2020-07-23 19:01, Lasse Langwadt Christensen wrote:
torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2 months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail, and my
go-to floating ground generator is getting scarce.   razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf


Awesome, thanks!  It has the same pinout, and for lower supply voltages
it might well be interchangeable.  I\'ll get some and see.

Cheers

Phil Hobbs


Incidentally it\'s cool how the latest revision of the TCA0372 datasheet
was like literally yesterday and it seems no one has noticed the output
stage as drawn doesn\'t make sense...

https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

I did notice the output on the block diagram made no sense the way
it is drawn, I just assumed some drew an arrow wrong on a transistor
and no one cared

it seems it been that way at least back to the Motorola data sheet I
found dated 1996


Even if they drew the upper stage as a regular Darlington it\'s probably
not a very good representation of the output stage, no ballast resistors
in the emitters and three diode drops but they describe \"zero-deadband
crossover distortion.\" Is the slew-rate symmetric?

doesn\'t look symmetric on fig7

three diodes should match an darlington and compound pair no?

The dual-Sziklai totem pole clearly wouldn\'t work as drawn, but it does
suggest the actual performance of the TCA0372--it pulls closer to the
positive rail than your old-school Darlington op amp output. (The lower
limit is much more Darlington-ish.)

so that bottom should be a darlington and the top Sziklai ?

 

[Lasse Langwadt Christensen]

fredag den 24. juli 2020 kl. 03.48.09 UTC+2 skrev Phil Hobbs:

On 2020-07-23 21:34, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 03.22.53 UTC+2 skrev bitrex:
On 7/23/2020 8:55 PM, Lasse Langwadt Christensen wrote:
fredag den 24. juli 2020 kl. 02.32.21 UTC+2 skrev bitrex:
On 7/23/2020 7:24 PM, Phil Hobbs wrote:
On 2020-07-23 19:01, Lasse Langwadt Christensen wrote:
torsdag den 23. juli 2020 kl. 20.15.24 UTC+2 skrev Phil Hobbs:
ON still lists the TCA0372 power op amp as active, but total distributor
stock is less than 1k pieces and the quoted lead time is 6-1/2 months!

Here I\'m trying to hang a couple of ADA4817s off a 20-V rail, and my
go-to floating ground generator is getting scarce.   razzafrazza%$&@!!


for 20V wouldn\'t this be an alternative?

https://www.st.com/resource/en/datasheet/l2720w.pdf


Awesome, thanks!  It has the same pinout, and for lower supply voltages
it might well be interchangeable.  I\'ll get some and see.

Cheers

Phil Hobbs


Incidentally it\'s cool how the latest revision of the TCA0372 datasheet
was like literally yesterday and it seems no one has noticed the output
stage as drawn doesn\'t make sense...

https://www.onsemi.com/pub/Collateral/TCA0372-D.PDF

I did notice the output on the block diagram made no sense the way
it is drawn, I just assumed some drew an arrow wrong on a transistor
and no one cared

it seems it been that way at least back to the Motorola data sheet I
found dated 1996


Even if they drew the upper stage as a regular Darlington it\'s probably
not a very good representation of the output stage, no ballast resistors
in the emitters and three diode drops but they describe \"zero-deadband
crossover distortion.\" Is the slew-rate symmetric?

doesn\'t look symmetric on fig7

three diodes should match an darlington and compound pair no?

The dual-Sziklai totem pole clearly wouldn\'t work as drawn, but it does
suggest the actual performance of the TCA0372--it pulls closer to the
positive rail than your old-school Darlington op amp output. (The lower
limit is much more Darlington-ish.)

so that bottom should be a darlington and the top Sziklai ?