[volt-nuts] LTZ1000 reference appnote question

[Fabio Eboli]

Mitch,are you referring to startup behaviour,
like Bob Smither suggests?

Just now I was trying to imagine the startup
(it's too late for firing up ltspice, I have to sleep :) )
and I was thinking that on startup both inputs
are zero and output can take both ways: go down (remain approx zero)
or go up, depending on input offset.
Is this correct?

If so what determines the correct startup
of the circuit?

Until the output diode is not forward biased
the opamp has no feedback and the output should amplify
any input noise some million times (open loop gain),
so I imagine that is only waiting that the noise on
inputs will steer the output the rignt way to forward-bias
the diode and start the reference.
Does all this makes sense?

Fabio.

Mitch Van Ochten <mitch at vincentelectronics.com> ha scritto:

> Positive input voltage range for an LT1006 is typically 1.2V below  
> the positive rail.
>
> mitch
>
>
> ----- Original Message ----- From: "Fabio Eboli" <fabioeb at quipo.it>
> To: <volt-nuts at febo.com>
> Sent: Wednesday, November 07, 2012 7:02 PM
> Subject: [volt-nuts] LTZ1000 reference appnote question
>
>
>> Hello, in this thread on eevblog:
>>
>> http://www.eevblog.com/forum/projects-designs-and-technical-stuff/does-anyone-know-what-this-diode-is-for/
>>
>> a guy named DiligentMinds.com asked the question
>> about why there is a 1N4148 diode on the output of
>> the opamp in the LTZ1000 reference circuit, the one
>> designed by Jim William in the appnotes, that can
>> also be seen on the first page of the datasheet:
>>
>> http://cds.linear.com/images/product/1203_app_1.JPG
>>
>> Now I'm curious,
>> anybody knows the answer?
>>
>> Thanks,
>> Fabio.
>>
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