bandgap voltages

The AVR internal bandgap is 1.1V. So it should be possible with a discrete.

Possibly the band gap of silicon (1.12eV)?

A Ge one should be possible at around 0.7V.

The reference in the LM10 is about 200mV but it requires a higher voltage to power it (about 1.1V).

Best regards, Spehro Pefhany

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A (standard) straight vbe + NkT/q stack always gives around 1.25V ±

However, if you have a low-VDD/low-current requirement (as I often do), you can make them anything you want by doing current mirror tricks.

But there's still the limitation that it takes around 1.4V VDD to run it.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
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Is the reference at the bandgap because of some fundamental physical reason, though, or just by chance?

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

That's where the Vbe drift cancels out the PTAT drift. It varies a bit with the current density in the Vbe.

Cheers,

Phil Hobbs

Not by chance.. but it's not exact. There's a simple derivation in this presentation:

Best regards, Spehro Pefhany

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"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
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As i understand it, yes; it is the "definition" (actually an un-achieveable limit point) that "sets" that value. Mr Pease has an elegant explaination.

One of my guys just pointed this out to me:

I wonder how they do it.

John

Interesting. The usual parabolic tempco curve for a bandgap is inverted. Looks like it would overcorrect a bit if you put it in series with the output of a TL431 to get 1.5V.

Best regards, Spehro Pefhany

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"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
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Maybe something like US6380723...

That appears to describe 3-terminal refs that need about 1.2 volts to power them. The ADI thing is a 2-terminal, 1-volt shunt reg.

CMOS? SiGe? Some new trick?

They may have a patent, too.

John

The noise number makes it look like a bandgap reference based design.

1V is enough that an op-amp of sorts can be used. I remember reading a paper on a topology that leads to "op-amps" down to 0.8V The op-amp was really a Norton amplifier with resistors built in.

Perhaps, but I doubt that Analog Devices has that particular configuration.

Note the 100uA _minimum_ current... there's a lot of circuitry in there.

"Shunt" allows the lower voltage operation.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
         America: Land of the Free, Because of the Brave

I'm surprised no one's mentioned the LM10 -- 200mV:

One of the Bobs wrote it up somewhere, I think.

Cheers, James Arthur

James Arthur a écrit :

I think Spehro did.

--
Thanks,
Fred.

Ahh, right you are. Missed that. Thanks for pointing it out.

Both Bobs wrote it up, actually. Widlar's account is here:

Cheers, James Arthur

Minimum supply is 1.2V

I can make a 100mV reference if you want (at the same minimum supply :-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
         America: Land of the Free, Because of the Brave

Ask the Czar of Bandgaps:

There are ones that are lower, 0.8V seems popular with low output voltage regs, like the MAX1806 I'm using at the moment.

Dave.

But that needs a 2.25 volt minimum supply. It's easy to make a 1.25 volt bandgap reference and then divide it down, to microvolts if required. I'm interested in lower-voltage 2-terminal shunt references.

John