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Difference Amp.

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  Difference Amp. George Herold <gherold@teachspin.com> - 2017-02-07 12:56 -0800
    Re: Difference Amp. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-07 16:40 -0500
      Re: Difference Amp. gghero27@gmail.com - 2017-02-07 17:47 -0800
        Re: Difference Amp. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-08 11:45 -0500
          Re: Difference Amp. George Herold <gherold@teachspin.com> - 2017-02-08 10:58 -0800
            Re: Difference Amp. Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-08 12:20 -0700
              Re: Difference Amp. Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-08 12:34 -0700
                Re: Difference Amp. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-08 16:09 -0500
                  Re: Difference Amp. Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-08 14:12 -0700
                    Re: Difference Amp. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-08 16:15 -0500
                      Re: Difference Amp. Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-08 14:21 -0700
                        Re: Difference Amp. George Herold <gherold@teachspin.com> - 2017-02-08 16:28 -0800
            Re: Difference Amp. Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-08 16:08 -0500
      Re: Difference Amp. gghero27@gmail.com - 2017-02-07 17:47 -0800
    Re: Difference Amp. sdy <sdeyoreo@hotmail.com> - 2017-02-07 16:20 -0800
      Re: Difference Amp. gghero27@gmail.com - 2017-02-07 17:50 -0800
        Re: Difference Amp. John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-08 12:45 -0800
    Re: Difference Amp. John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-07 17:22 -0800
      Re: Difference Amp. Winfield Hill <hill@rowland.harvard.edu> - 2017-02-07 17:40 -0800
        Re: Difference Amp. Robert Latest <boblatest@yahoo.com> - 2017-02-08 18:10 +0000
          Re: Difference Amp. Winfield Hill <hill@rowland.harvard.edu> - 2017-02-08 12:06 -0800
            Re: Difference Amp. Robert Latest <boblatest@yahoo.com> - 2017-02-09 17:55 +0000
    Re: Difference Amp. Kamen Lilov <kamenl@gmail.com> - 2017-02-08 11:25 -0800
      Re: Difference Amp. George Herold <gherold@teachspin.com> - 2017-02-08 12:41 -0800
        Re: Difference Amp. George Herold <gherold@teachspin.com> - 2017-02-08 12:47 -0800
      Re: Difference Amp. krw@notreal.com - 2017-02-08 20:43 -0500

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#446846

Robert Latest wrote...
>
>Winfield Hill wrote:
>>
>>  Right.  These parts aren't going to disappear.
>>  Most of the popular versions shown in our 1989
>>  2nd edition are still going strong, and will
>>  for decades to come.
>
> Until it's the last low-volume product that won't
> be transferred onto the next wafer size or a
> different fab.

 I think TI / Burr-Brown have already done such a
 transfer for these parts.  Precision difference
 amplifiers are visible high-profit items.


-- 
 Thanks,
    - Win

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#447035

Winfield Hill wrote:

>  I think TI / Burr-Brown have already done such a
>  transfer for these parts.  Precision difference
>  amplifiers are visible high-profit items.

Good for them. I'm just saying: When doing, for instance, a wafer size
transfer there is always that last low-volume product that's neither worth
keeping the old line alive for, nor transferring it, no matter margin or
visibility. I have a 100->150mm transfer behind me and am in the middle of
going to 200mm in a NXP (now Nexperia) waferfab, so I've been down that
road. Of course it's mostly automotive customers clinging to the old
products.

robert

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#446839

On Tuesday, February 7, 2017 at 10:56:21 PM UTC+2, George Herold wrote:
> Hmm that might be my only question.  Would you use these instead 
> of an opamp and 0.1% R's?   

No, because

a) most of them are trimmed to way under 0.1%

b) I had the misfortune of needing 0.1% resistors recently for a specific application, and four resistors definitely cost more than a single differential opamp

c) I think while they're trimming them, they are also trimming some extra resistors that play in the compensation network and you can't do that outside the chip

d) Those resistors stay at the chip temperature and the nulling circuitry takes the tempco into account

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#446851

On Wednesday, February 8, 2017 at 2:25:28 PM UTC-5, Kamen Lilov wrote:
> On Tuesday, February 7, 2017 at 10:56:21 PM UTC+2, George Herold wrote:
> > Hmm that might be my only question.  Would you use these instead 
> > of an opamp and 0.1% R's?   
> 
> No, because
> 
> a) most of them are trimmed to way under 0.1%
> 
> b) I had the misfortune of needing 0.1% resistors recently for a specific application, and four resistors definitely cost more than a single differential opamp
> 
> c) I think while they're trimming them, they are also trimming some extra resistors that play in the compensation network and you can't do that outside the chip
> 
> d) Those resistors stay at the chip temperature and the nulling circuitry takes the tempco into account

Thanks Kamen,  I've been using these susumu 0.1% R's.. they use to be about 
$0.2 each (at hundreds quantity) but now you can get them for about $0.10.  
https://octopart.com/search?q=RG2012P-103-B-T5

George H. 

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#446853

On Wednesday, February 8, 2017 at 3:41:22 PM UTC-5, George Herold wrote:
> On Wednesday, February 8, 2017 at 2:25:28 PM UTC-5, Kamen Lilov wrote:
> > On Tuesday, February 7, 2017 at 10:56:21 PM UTC+2, George Herold wrote:
> > > Hmm that might be my only question.  Would you use these instead 
> > > of an opamp and 0.1% R's?   
> > 
> > No, because
> > 
> > a) most of them are trimmed to way under 0.1%
> > 
> > b) I had the misfortune of needing 0.1% resistors recently for a specific application, and four resistors definitely cost more than a single differential opamp
> > 
> > c) I think while they're trimming them, they are also trimming some extra resistors that play in the compensation network and you can't do that outside the chip
> > 
> > d) Those resistors stay at the chip temperature and the nulling circuitry takes the tempco into account
> 
> Thanks Kamen,  I've been using these susumu 0.1% R's.. they use to be about 
> $0.2 each (at hundreds quantity) but now you can get them for about $0.10.  
> https://octopart.com/search?q=RG2012P-103-B-T5
> 
> George H.

Oh and a colleague pointed me to these in through hole.
https://octopart.com/search?q=mfp-25brd52-10k

GH

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#446944

On Wed, 8 Feb 2017 11:25:19 -0800 (PST), Kamen Lilov
<kamenl@gmail.com> wrote:

>On Tuesday, February 7, 2017 at 10:56:21 PM UTC+2, George Herold wrote:
>> Hmm that might be my only question.  Would you use these instead 
>> of an opamp and 0.1% R's?   
>
>No, because
>
>a) most of them are trimmed to way under 0.1%
>
>b) I had the misfortune of needing 0.1% resistors recently for a specific application, and four resistors definitely cost more than a single differential opamp

Depends on quantities.  I think we pay about 100x for a 0.1% resistor
than we do for a 1% resistor but that doesn't make it exactly
expensive (relative to an amplifier).  I'm trying to find some small
(0402 equivalent) arrays.

>c) I think while they're trimming them, they are also trimming some extra resistors that play in the compensation network and you can't do that outside the chip
>
>d) Those resistors stay at the chip temperature and the nulling circuitry takes the tempco into account

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