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OK, but the little opamp works better. Same number of parts, much
smaller, more stable, uses available values. That\'s the game here.
OK, but the little opamp works better. Same number of parts, much
smaller, more stable, uses available values. That\'s the game here.
OK, but the little opamp works better. Same number of parts, much
smaller, more stable, uses available values. That\'s the game here.
On Sun, 14 Nov 2021 22:14:47 +0000, TTman <kraken.sankey@gmail.com
wrote:
On 14/11/2021 18:27, jlarkin@highlandsniptechnology.com wrote:
On Sun, 14 Nov 2021 17:59:06 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:
On a sunny day (Sun, 14 Nov 2021 09:39:03 -0800) it happened
jlarkin@highlandsniptechnology.com wrote in
1ch2pgh4echute3tflmia84j7uosmor4rv@4ax.com>:
On Sun, 14 Nov 2021 17:11:29 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:
On a sunny day (Sun, 14 Nov 2021 08:39:13 -0800) it happened
jlarkin@highlandsniptechnology.com wrote in
54e2pgl0ir9ucjhtrcq35c0dj7pkadrgf8@4ax.com>:
Once you have a few resistors on a schematic, it\'s tempting to do what
you want using existing values. That reduces the BOM and the
pick-and-place setup. There are far more possibilities if you are
willing to compromise things some, or put resistors in series and
parallel. This is a 4-page schematic with 9 different resistors. Doing
this is an enormous PITA.
https://www.dropbox.com/s/aozh6m6mmmik6lb/T502_Parts.jpg?raw=1
Saved a DAC reference chip! Actually, having the DAC voltage
ratiometric on +15 is a benefit here.
That opamp should be stable with the tantalum load and a 1u ceramic at
the DAC, but I\'ll verify that.
Or a second LM317 for the +3V?
Yuk! That would involve an entire new chain of value juggling.
Really?
The resistor ratio needs to be 1.4:1. I can get 3.125 volts with three
resistors.
What I do not get is: you sell expensive things in low quantity and try to save on a trimpot?
Trimpots are expensive and need manual turning. DACs are automated and
can have cal factors stored in cal tables. I\'m using 16-bit DACs and
there are no 16-bit trimpots.
Some of my customers absolutely forbid trimpots, which I think is
extreme. Once in a while they make sense. They say that if there\'s a
pot, their techs will turn it.
or waste board space with funny resistor combinations?
I have space on this one for a few more 0603s. It\'s inefficient to
load a reel onto the pick-and-place just for one resistor.
The LM317 is huge.
I mean I use 3 resistors to get a LM317 to output some specific voltage all the time..
mostly different ones.
Sure you can use 1 Ohm resistors to do most things, but then you need many,,,,
10 Ohm would work too here.
The +15 charges a timing ramp through resistors, and the DAC feeds
some timing comparators, so it\'s nice if they are ratiometric. 317\'s
are not very good references.
Data sheets suggest that an LM317 can\'t make 3 volts from 5 volts, so
I\'d have to power it off +24.
Power it from the 15V you made with the first one.
OK, but the little opamp works better. Same number of parts, much
smaller, more stable, uses available values. That\'s the game here.
Pots are your enemy...
When I see a schematic full of trimpots, it\'s a sure bet that the
author doesn\'t understand things.
The Review Of Scientific Instruments is full of trimpots. And
diffamps. And current mirrors.
On Sun, 14 Nov 2021 22:14:47 +0000, TTman <kraken.sankey@gmail.com
wrote:
On 14/11/2021 18:27, jlarkin@highlandsniptechnology.com wrote:
On Sun, 14 Nov 2021 17:59:06 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:
On a sunny day (Sun, 14 Nov 2021 09:39:03 -0800) it happened
jlarkin@highlandsniptechnology.com wrote in
1ch2pgh4echute3tflmia84j7uosmor4rv@4ax.com>:
On Sun, 14 Nov 2021 17:11:29 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:
On a sunny day (Sun, 14 Nov 2021 08:39:13 -0800) it happened
jlarkin@highlandsniptechnology.com wrote in
54e2pgl0ir9ucjhtrcq35c0dj7pkadrgf8@4ax.com>:
Once you have a few resistors on a schematic, it\'s tempting to do what
you want using existing values. That reduces the BOM and the
pick-and-place setup. There are far more possibilities if you are
willing to compromise things some, or put resistors in series and
parallel. This is a 4-page schematic with 9 different resistors. Doing
this is an enormous PITA.
https://www.dropbox.com/s/aozh6m6mmmik6lb/T502_Parts.jpg?raw=1
Saved a DAC reference chip! Actually, having the DAC voltage
ratiometric on +15 is a benefit here.
That opamp should be stable with the tantalum load and a 1u ceramic at
the DAC, but I\'ll verify that.
Or a second LM317 for the +3V?
Yuk! That would involve an entire new chain of value juggling.
Really?
The resistor ratio needs to be 1.4:1. I can get 3.125 volts with three
resistors.
What I do not get is: you sell expensive things in low quantity and try to save on a trimpot?
Trimpots are expensive and need manual turning. DACs are automated and
can have cal factors stored in cal tables. I\'m using 16-bit DACs and
there are no 16-bit trimpots.
Some of my customers absolutely forbid trimpots, which I think is
extreme. Once in a while they make sense. They say that if there\'s a
pot, their techs will turn it.
or waste board space with funny resistor combinations?
I have space on this one for a few more 0603s. It\'s inefficient to
load a reel onto the pick-and-place just for one resistor.
The LM317 is huge.
I mean I use 3 resistors to get a LM317 to output some specific voltage all the time..
mostly different ones.
Sure you can use 1 Ohm resistors to do most things, but then you need many,,,,
10 Ohm would work too here.
The +15 charges a timing ramp through resistors, and the DAC feeds
some timing comparators, so it\'s nice if they are ratiometric. 317\'s
are not very good references.
Data sheets suggest that an LM317 can\'t make 3 volts from 5 volts, so
I\'d have to power it off +24.
Power it from the 15V you made with the first one.
OK, but the little opamp works better. Same number of parts, much
smaller, more stable, uses available values. That\'s the game here.
Pots are your enemy...
When I see a schematic full of trimpots, it\'s a sure bet that the
author doesn\'t understand things.
The Review Of Scientific Instruments is full of trimpots. And
diffamps. And current mirrors.
On Sun, 14 Nov 2021 22:14:47 +0000, TTman <kraken.sankey@gmail.com
wrote:
On 14/11/2021 18:27, jlarkin@highlandsniptechnology.com wrote:
On Sun, 14 Nov 2021 17:59:06 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:
On a sunny day (Sun, 14 Nov 2021 09:39:03 -0800) it happened
jlarkin@highlandsniptechnology.com wrote in
1ch2pgh4echute3tflmia84j7uosmor4rv@4ax.com>:
On Sun, 14 Nov 2021 17:11:29 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:
On a sunny day (Sun, 14 Nov 2021 08:39:13 -0800) it happened
jlarkin@highlandsniptechnology.com wrote in
54e2pgl0ir9ucjhtrcq35c0dj7pkadrgf8@4ax.com>:
Once you have a few resistors on a schematic, it\'s tempting to do what
you want using existing values. That reduces the BOM and the
pick-and-place setup. There are far more possibilities if you are
willing to compromise things some, or put resistors in series and
parallel. This is a 4-page schematic with 9 different resistors. Doing
this is an enormous PITA.
https://www.dropbox.com/s/aozh6m6mmmik6lb/T502_Parts.jpg?raw=1
Saved a DAC reference chip! Actually, having the DAC voltage
ratiometric on +15 is a benefit here.
That opamp should be stable with the tantalum load and a 1u ceramic at
the DAC, but I\'ll verify that.
Or a second LM317 for the +3V?
Yuk! That would involve an entire new chain of value juggling.
Really?
The resistor ratio needs to be 1.4:1. I can get 3.125 volts with three
resistors.
What I do not get is: you sell expensive things in low quantity and try to save on a trimpot?
Trimpots are expensive and need manual turning. DACs are automated and
can have cal factors stored in cal tables. I\'m using 16-bit DACs and
there are no 16-bit trimpots.
Some of my customers absolutely forbid trimpots, which I think is
extreme. Once in a while they make sense. They say that if there\'s a
pot, their techs will turn it.
or waste board space with funny resistor combinations?
I have space on this one for a few more 0603s. It\'s inefficient to
load a reel onto the pick-and-place just for one resistor.
The LM317 is huge.
I mean I use 3 resistors to get a LM317 to output some specific voltage all the time..
mostly different ones.
Sure you can use 1 Ohm resistors to do most things, but then you need many,,,,
10 Ohm would work too here.
The +15 charges a timing ramp through resistors, and the DAC feeds
some timing comparators, so it\'s nice if they are ratiometric. 317\'s
are not very good references.
Data sheets suggest that an LM317 can\'t make 3 volts from 5 volts, so
I\'d have to power it off +24.
Power it from the 15V you made with the first one.
OK, but the little opamp works better. Same number of parts, much
smaller, more stable, uses available values. That\'s the game here.
Pots are your enemy...
When I see a schematic full of trimpots, it\'s a sure bet that the
author doesn\'t understand things.
The Review Of Scientific Instruments is full of trimpots. And
diffamps. And current mirrors.
On Sunday, November 14, 2021 at 2:14:53 PM UTC-8, TTman wrote:
On 14/11/2021 18:27, jla...@highlandsniptechnology.com wrote:
I have space on this one for a few more 0603s. It\'s inefficient to
load a reel onto the pick-and-place just for one resistor.
Pots are your enemy...
When mailorder is slow, and you have a triangle file and carbon comp
resistor in play, it\'s time to declare armistice or maybe even peace.
Remember, after filing the notch, to use some nail polish for
sealing that surface... or job it out to a cosmetology shop.
On Sunday, November 14, 2021 at 2:14:53 PM UTC-8, TTman wrote:
On 14/11/2021 18:27, jla...@highlandsniptechnology.com wrote:
I have space on this one for a few more 0603s. It\'s inefficient to
load a reel onto the pick-and-place just for one resistor.
Pots are your enemy...
When mailorder is slow, and you have a triangle file and carbon comp
resistor in play, it\'s time to declare armistice or maybe even peace.
Remember, after filing the notch, to use some nail polish for
sealing that surface... or job it out to a cosmetology shop.
When I see a schematic full of trimpots, it\'s a sure bet that the
author doesn\'t understand things.
The Review Of Scientific Instruments is full of trimpots. And
diffamps. And current mirrors.
When I see a schematic full of trimpots, it\'s a sure bet that the
author doesn\'t understand things.
The Review Of Scientific Instruments is full of trimpots. And
diffamps. And current mirrors.
On a sunny day (Sun, 14 Nov 2021 14:22:45 -0800) it happened
jlarkin@highlandsniptechnology.com wrote in
ss23pgp37oil6tqviok9jpgaepnd9jn6lc@4ax.com>:
When I see a schematic full of trimpots, it\'s a sure bet that the
author doesn\'t understand things.
In the older days trimpots were common for opamp offset compensation in many precision circuits.
Not sure if modern opamps still have offset errors?
The Review Of Scientific Instruments is full of trimpots. And
diffamps. And current mirrors.
Its the same with variable inductors, radios used to be full of those,
now everything is done in sillycon.
rtl-sdr USB stick as example.
On a sunny day (Sun, 14 Nov 2021 14:22:45 -0800) it happened
jlarkin@highlandsniptechnology.com wrote in
ss23pgp37oil6tqviok9jpgaepnd9jn6lc@4ax.com>:
When I see a schematic full of trimpots, it\'s a sure bet that the
author doesn\'t understand things.
In the older days trimpots were common for opamp offset compensation in many precision circuits.
Not sure if modern opamps still have offset errors?
The Review Of Scientific Instruments is full of trimpots. And
diffamps. And current mirrors.
Its the same with variable inductors, radios used to be full of those,
now everything is done in sillycon.
rtl-sdr USB stick as example.
On 15/11/2021 16:34, whit3rd wrote:
On Sunday, November 14, 2021 at 2:14:53 PM UTC-8, TTman wrote:
On 14/11/2021 18:27, jla...@highlandsniptechnology.com wrote:
I have space on this one for a few more 0603s. It\'s inefficient to
load a reel onto the pick-and-place just for one resistor.
Pots are your enemy...
When mailorder is slow, and you have a triangle file and carbon comp
resistor in play, it\'s time to declare armistice or maybe even peace.
Remember, after filing the notch, to use some nail polish for
sealing that surface... or job it out to a cosmetology shop.
Barbarian, using a triangle file, think of the mechanical stress
concentration begging it to snap in half. Use a round chainsaw
sharpening file or round needle file at least! I\'d even consider
drilling a few small holes part way through it would be more humane.
On 15/11/2021 16:34, whit3rd wrote:
On Sunday, November 14, 2021 at 2:14:53 PM UTC-8, TTman wrote:
On 14/11/2021 18:27, jla...@highlandsniptechnology.com wrote:
I have space on this one for a few more 0603s. It\'s inefficient to
load a reel onto the pick-and-place just for one resistor.
Pots are your enemy...
When mailorder is slow, and you have a triangle file and carbon comp
resistor in play, it\'s time to declare armistice or maybe even peace.
Remember, after filing the notch, to use some nail polish for
sealing that surface... or job it out to a cosmetology shop.
Barbarian, using a triangle file, think of the mechanical stress
concentration begging it to snap in half. Use a round chainsaw
sharpening file or round needle file at least! I\'d even consider
drilling a few small holes part way through it would be more humane.
On Sunday, November 14, 2021 at 10:27:30 AM UTC-8, jla...@highlandsniptechnology.com wrote:
OK, but the little opamp works better. Same number of parts, much
smaller, more stable, uses available values. That\'s the game here.
It\'s happy driving 4.7uF to ground?
-- john, KE5FX
I haven\'t seen a carbon comp resistor in years.
I haven\'t seen a carbon comp resistor in years.
On Sunday, November 14, 2021 at 10:27:30 AM UTC-8, jla...@highlandsniptechnology.com wrote:
OK, but the little opamp works better. Same number of parts, much
smaller, more stable, uses available values. That\'s the game here.
It\'s happy driving 4.7uF to ground?
-- john, KE5FX
On Mon, 15 Nov 2021 15:15:25 GMT, Jan Panteltje
pNaOnSt...@yahoo.com> wrote:
On a sunny day (Sun, 14 Nov 2021 14:22:45 -0800) it happened
jla...@highlandsniptechnology.com wrote in
ss23pgp37oil6tqvi...@4ax.com>:
When I see a schematic full of trimpots, it\'s a sure bet that the
author doesn\'t understand things.
In the older days trimpots were common for opamp offset compensation in many precision circuits.
Not sure if modern opamps still have offset errors?
Some have a few uV offset and a few nV/degc drifts.
On Mon, 15 Nov 2021 15:15:25 GMT, Jan Panteltje
pNaOnSt...@yahoo.com> wrote:
On a sunny day (Sun, 14 Nov 2021 14:22:45 -0800) it happened
jla...@highlandsniptechnology.com wrote in
ss23pgp37oil6tqvi...@4ax.com>:
When I see a schematic full of trimpots, it\'s a sure bet that the
author doesn\'t understand things.
In the older days trimpots were common for opamp offset compensation in many precision circuits.
Not sure if modern opamps still have offset errors?
Some have a few uV offset and a few nV/degc drifts.