Same here. So simple it's pathetic. Tells me that your average engineer has no clue of fundamental feedback theory.
Yes :-(
Turns out that this very post is to charge a battery. Why an LDO was chosen I have no clue. The obvious solution (at least to me) is a simple current source plus a voltage cut-off. Current sources rarely have stability issues, and can be made low-headroom if you know what you are doing. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| 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.
I don't see ANY of Phil's posts, so my apologies.
The only difference between a depletion FET (sometimes called a "native" device") is the threshold... so my equation applies always.
Thus the depletion FET will become a resistor at a small headroom as well.
I've not seen a schematic. Can you provide a link/message-ID? ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| 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.
Actually they are there... "native" device. They just don't appear in the available device list unless you ask. I use them mostly for start-up devices in reference circuits. Then they turn off... giving me better PSRR from my bandgaps. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| 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.
All three terminals "free" ??
I don't think so... top collector??
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| 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.
I can't remember which thread it was and I can't find it. The circuit was one to provide power from a thermocouple in a candle. It may have been lighting an LED, lol.
-- Rick
[snip]
Shhhhh! Don't tell Moonbeam, he'll sign a law requiring LED lighting powered by a candle >:-} ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| 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.
The natural/native 0Vt mos are great as "beta" helpers in a bipolar current mirror. i.e. to get the low 1/f noise of the bipolar, but effectively zero base current error of a mosfet.
Kevin Aylward
Aha! Great idea! I'll have to try it. Sonnuva gun, why didn't I think of that >:-} ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| 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.
Hmm, interesting. I thought those were usually JFETs, but that might be in planar bipolar processes.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
So you use the FET as a follower on one of the collectors, to drive the two bases? I see, the input-side BJT has enough voltage gain that the loop takes out the FET's noise. That works well the other way round in TIAs--a bit of local feedback will give you the bipolar's drive with the JFET's noise.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...
On a somewhat related tangent, what ever happened to Intel's HMOS process (5V NMOS with depletion mode pullups) -- is there something like that still available, and is it at all useful?
I know, unlimited N/PMOS is probably infinitely more useful ;-)
Tim
-- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com
On Sun, 5 Oct 2014 16:18:08 -0500, "Tim Williams" Gave us:
Think about how long 5 volt logic swings take.
Now, imagine that being one reason why such potentials were reduced over the years. It was not merely power consumption factors.
Buzzing along a 3.3 volt square wave can be pushed pretty fast. Buzzing along a 5 volt swing square wave runs into limitations which clamp maximum attainable speed quite quickly.
The word for today is "ring".
The game, now-a-days, is multi-voltage processes. A chip might have a
1.8V "core" (size and speed advantages), a 3.3V I/O (to talk to off-the-shelf peripherals), and a 30V power stage to drive all kinds of interesting things. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| 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.
Same here. So simple it's pathetic. Tells me that your average engineer has no clue of fundamental feedback theory.
Yes :-(
Turns out that this very post is to charge a battery. Why an LDO was chosen I have no clue. The obvious solution (at least to me) is a simple current source plus a voltage cut-off. Current sources rarely have stability issues, and can be made low-headroom if you know what you are doing.
...Jim Thompson
In the ASIC design we need a li bat charger with a input similar to a LDO. The input will range from 3.6V to 9.0V with most operation at 4.0 V. We did not have room for the inductor of a Buck-Boost, so this limits some operating range. What is the lowest headroom normally attainable in a 30mA CC device with suitable HF rejection to limit bat AC current to
Maybe there is a concern of RFI ?
Jamie
Maybe there is a concern of RFI ?
Jamie
The charging current is 30mA but the noise current drove it to 100mApk at
700KHz. This is implanted under the skin so we worry about heating and bat life.Cheers, Harry
Harry,
A half volt of 700KHz ripple is a lot easier to kill before it hits the chip, given the kinds of capacitors available nowadays to do just that. Requirement for local decoupling on inputs of ASICS is something designers are used to dealing with, so why not just make them do it? End users will likely just wimp out and apply an external LDO, anyways, if there's the slightest chance that a ($$)chip's performance will become unpredictable.
Getting internal load regulation will be hard enough, as is.
For really good dynamic load regulation a lossy ripple regulator on the output node can be run on the same regulation loop - but this thing is lossy already, so who's to complain?
RL
It is about real estate. Input and output filters take up room and suck dropout voltage. A Proper design should be able to do this in silicon.
Cheers, Harry
I have LED drivers running at 25mA, on and off in 20ns, with 0.3V head-room; but I haven't tested them for PSRR under conditions like you have. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| 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.
I'm having trouble visualizing how this would be connected and why it is better than a Wilson or a Cascode. Could you post an ASCII drawing or even better a LTspice file to show how it is connected?
Wow... hope I never have to have it implanted... just sayin'...
Tim
-- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com
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