Yep. Judging from the input bias specs, they've got some HUGE input devices there. That's OK for a few OpAmps, but not practical for an SoC (my sonar chip size was ~10mm x 10.5mm). Bipolar devices can be much smaller for the same noise performance. My sonar chip had ~6nV/rt-Hz (including noise from the 1K source impedance) at maximum gain... rising as the gain decreases (TVG). Current noise was ~1pA/rt-Hz. ...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 |
I love to cook with wine. Sometimes I even put it in the food.
[snip] [snip] [snip]
Looked it up... L=1u W=1600u !! ...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
Even better:
It's 65 cents at 1K, a tad less than the ADI part.
John
16nV/sqrt(Hz) at 40Hz typical, vs. more like 1nV/sqrt(Hz) for a good bipolar op-amp operating from a low source impedance.
imploding
I didn't notice that... hiding the 1/f ;-)
I'm working the other end of the spectrum right now... all CMOS, rail-to-rail input AND output,
imploding
Never said it could compete with a low noise bjt opamp.
But 8nV/rtHz noise floor isn't common for cmos opamps, which often are at least 5 times that high. And a 140Hz fc with a 8nV/rtHz is pretty good too, as it is ordinary at least as high, but with a 5-10 times higher noise floor.
Sure it can't compete, but so can't LN BJT opamps with my 200pV/rtHz preamp.
Still, the AD8605 is amazing for a CMOS opamp. (and I like the tiny 5 balls WLCSP, despite they goofed the pinout).
-- Thanks, Fred.
Jim Thompson a écrit :
Come on, you should know better...
-- Thanks, Fred.
That's W=1.6mm, longer than most chips edge dimension. So the input stage dominates the chip area. Not that unusual, check out...
The pass device takes up 2/3 of the chip. ...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 |
I love to cook with wine. Sometimes I even put it in the food.
imploding
I suspect the input stage is actually JFET's, or gate-enhanced lateral bipolar devices. The input current seems high for MOS. ...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 |
I love to cook with wine. Sometimes I even put it in the food.
imploding
BIG input JFETs (in paraellel?)
Yeah, it's pretty good alright. A far cry from early CMOS amplifiers.
imploding
Yep, a 6 x IF3602 (duals) LPT input stage running a total 240mA tail current.
About 2nV/rt Hz at... 0.1Hz and 1nV/rtHz at 1Hz with a nice low input current noise. Not that it matters regarding the input load, but the measured signal is biased so a series cap was required, which carried its share of funny design consequences...
-- Thanks, Fred.
Yup, but what I meant is that vendors' macro models almost never (read never) reflect actual devices.
-- Thanks, Fred.
imploding
Yep, but the sc70 package is, well, terribly huge for my needs...
-- Thanks, Fred.
It might here, simply because they're trying to match the input noise curve. ...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 |
I love to cook with wine. Sometimes I even put it in the food.
imploding
It's available in SOT-23 and even in the huge SO-8 package.
I was looking at a board the other day and noticed how big an 0805 resistor looked. That's frightening.
John
We use AD8606s (dual 8605) as our go to opamp. We've started replacing them in one product with LMV852s. They're EMI hardened and do better in our 2.4GHz rich environment.
No, I haven't heard from Philippe since the project. I wish I had someone like him to work along side. He was chock full of useful knowledge.
As to the downhill bit, from a personal gain, it was a good thing. No baggage from the investors who thought that the old company could increase revenue by 6 times in a year period. They actually said this in a all hands meeting which quickly, but calmly, "ended" after I started to ask a few questions about their new business model. Nice to get back to a small company where I don't need to give silly talks to financial people who have no idea what a sonar is every year. Nice to only deal with current products instead of splitting my time up to support products still in production after 15 years.
-- Mark
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