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From: Jim Thompson on 22 Dec 2009 16:05
On Tue, 22 Dec 2009 15:35:17 -0500, Phil Hobbs
<pcdhSpamMeSenseless(a)electrooptical.net> wrote:

>On 12/22/2009 3:30 PM, Jim Thompson wrote:
>> On Tue, 22 Dec 2009 14:55:13 -0500, Phil Hobbs
>> <pcdhSpamMeSenseless(a)electrooptical.net> wrote:
>>
>>> On 8/29/2009 10:42 AM, Jim Thompson wrote:
>>>>>>>>>> "Michael Robinson"<nospam(a)billburg.com> wrote in message
>>>
>>> Since we're on voltage references, I notice that LTC has a really nice
>>> CMOS bandgap--the LTC6655--with<800 pV noise (0.01-10 Hz) and 2 ppm
>>> tempco in a 5V series reference with 300 mV dropout voltage.
>>>
>>> That's pretty good going. Now, bipolar bandgaps are horribly noisy
>>> because you have to put 20 dB gain on the delta-Vbe before adding it to
>>> the diode drop. How come CMOS bandgaps can be so much better?
>>>
>>> I normally think of CMOS as being much noisier than bipolar at low
>>> impedance levels and especially at low frequency, so the LTC6655's
>>> performance really surprised me.
>>>
>>> Any notion of how it works?
>>>
>>> Cheers
>>>
>>> Phil Hobbs
>>
>> I'll take a look after Christmas. Add an emergency repair event to
>> the shopping scramble and I'm behind :-(
>>
>> Skylight failed open... lever arms sliding in grooves failed. I
>> managed to disassemble it 16' up on a ladder and close it just before
>> the thunderstorm hit ;-)
>>
>> .... 66�F and pouring the rain ;-)
>>
>> ...Jim Thompson
>
>800 nV that is--still very good for a voltage reference. Merry
>Christmas, and may God bless you and your family even though you don't
>believe He exists. ;)

But I'm a great traditionalist. Celebrate everyone's holidays... they
all drink don't they ?:-)

Holidays are for children and grandchildren anyway!

Merry Christmas to all and to all a good night!

And we have a Hanukkah bush as well ;-)

Plus we've added a new event this year... "Meet the families" ;-)

>
>There's an old story told about Enrico Fermi--he had a horseshoe nailed
>above his front door. One of his colleagues said to him one day,
>"Enrico, surely you don't believe that ridiculous object is going to
>bring you good luck!" Fermi replied, "Of course not! But I am reliably
>informed that it will whether I believe in it or not."

Absolutely!

>
>Cheers
>
>Phil Hobbs
>
>Cheers
>
>Phil Hobbs

...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:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Help save the environment!
Please dispose of socialism properly!
From: John Larkin on 22 Dec 2009 16:24
On Tue, 22 Dec 2009 14:55:13 -0500, Phil Hobbs
<pcdhSpamMeSenseless(a)electrooptical.net> wrote:

>On 8/29/2009 10:42 AM, Jim Thompson wrote:
>>>>>>>> "Michael Robinson"<nospam(a)billburg.com> wrote in message
>
>Since we're on voltage references, I notice that LTC has a really nice
>CMOS bandgap--the LTC6655--with <800 pV noise (0.01-10 Hz) and 2 ppm
>tempco in a 5V series reference with 300 mV dropout voltage.
>
>That's pretty good going. Now, bipolar bandgaps are horribly noisy
>because you have to put 20 dB gain on the delta-Vbe before adding it to
>the diode drop. How come CMOS bandgaps can be so much better?
>
>I normally think of CMOS as being much noisier than bipolar at low
>impedance levels and especially at low frequency, so the LTC6655's
>performance really surprised me.
>
>Any notion of how it works?
>
>Cheers
>
>Phil Hobbs

ADR421 has been around a while and is almost as good, at around the
same price. I think it's a jfet thing.

Vref TCs in the low ppm range require corresponding resistors!

The Intersil floating-gate things are cool.

John

From: Phil Hobbs on 22 Dec 2009 14:55
On 8/29/2009 10:42 AM, Jim Thompson wrote:
>>>>>>> "Michael Robinson"<nospam(a)billburg.com> wrote in message

Since we're on voltage references, I notice that LTC has a really nice
CMOS bandgap--the LTC6655--with <800 pV noise (0.01-10 Hz) and 2 ppm
tempco in a 5V series reference with 300 mV dropout voltage.

That's pretty good going. Now, bipolar bandgaps are horribly noisy
because you have to put 20 dB gain on the delta-Vbe before adding it to
the diode drop. How come CMOS bandgaps can be so much better?

I normally think of CMOS as being much noisier than bipolar at low
impedance levels and especially at low frequency, so the LTC6655's
performance really surprised me.

Any notion of how it works?

Cheers

Phil Hobbs

From: Jim Thompson on 22 Dec 2009 15:30
On Tue, 22 Dec 2009 14:55:13 -0500, Phil Hobbs
<pcdhSpamMeSenseless(a)electrooptical.net> wrote:

>On 8/29/2009 10:42 AM, Jim Thompson wrote:
>>>>>>>> "Michael Robinson"<nospam(a)billburg.com> wrote in message
>
>Since we're on voltage references, I notice that LTC has a really nice
>CMOS bandgap--the LTC6655--with <800 pV noise (0.01-10 Hz) and 2 ppm
>tempco in a 5V series reference with 300 mV dropout voltage.
>
>That's pretty good going. Now, bipolar bandgaps are horribly noisy
>because you have to put 20 dB gain on the delta-Vbe before adding it to
>the diode drop. How come CMOS bandgaps can be so much better?
>
>I normally think of CMOS as being much noisier than bipolar at low
>impedance levels and especially at low frequency, so the LTC6655's
>performance really surprised me.
>
>Any notion of how it works?
>
>Cheers
>
>Phil Hobbs

I'll take a look after Christmas. Add an emergency repair event to
the shopping scramble and I'm behind :-(

Skylight failed open... lever arms sliding in grooves failed. I
managed to disassemble it 16' up on a ladder and close it just before
the thunderstorm hit ;-)

..... 66�F and pouring the rain ;-)

...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:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Help save the environment!
Please dispose of socialism properly!
From: Phil Hobbs on 22 Dec 2009 15:35
On 12/22/2009 3:30 PM, Jim Thompson wrote:
> On Tue, 22 Dec 2009 14:55:13 -0500, Phil Hobbs
> <pcdhSpamMeSenseless(a)electrooptical.net> wrote:
>
>> On 8/29/2009 10:42 AM, Jim Thompson wrote:
>>>>>>>>> "Michael Robinson"<nospam(a)billburg.com> wrote in message
>>
>> Since we're on voltage references, I notice that LTC has a really nice
>> CMOS bandgap--the LTC6655--with<800 pV noise (0.01-10 Hz) and 2 ppm
>> tempco in a 5V series reference with 300 mV dropout voltage.
>>
>> That's pretty good going. Now, bipolar bandgaps are horribly noisy
>> because you have to put 20 dB gain on the delta-Vbe before adding it to
>> the diode drop. How come CMOS bandgaps can be so much better?
>>
>> I normally think of CMOS as being much noisier than bipolar at low
>> impedance levels and especially at low frequency, so the LTC6655's
>> performance really surprised me.
>>
>> Any notion of how it works?
>>
>> Cheers
>>
>> Phil Hobbs
>
> I'll take a look after Christmas. Add an emergency repair event to
> the shopping scramble and I'm behind :-(
>
> Skylight failed open... lever arms sliding in grooves failed. I
> managed to disassemble it 16' up on a ladder and close it just before
> the thunderstorm hit ;-)
>
> .... 66�F and pouring the rain ;-)
>
> ...Jim Thompson

800 nV that is--still very good for a voltage reference. Merry
Christmas, and may God bless you and your family even though you don't
believe He exists. ;)

There's an old story told about Enrico Fermi--he had a horseshoe nailed
above his front door. One of his colleagues said to him one day,
"Enrico, surely you don't believe that ridiculous object is going to
bring you good luck!" Fermi replied, "Of course not! But I am reliably
informed that it will whether I believe in it or not."

Cheers

Phil Hobbs

Cheers

Phil Hobbs
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