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From: firstname.lastname@example.org (Frank Miles)
Subject: Re: LED reverse leakage current
Date: 21 Nov 2002 19:57:34 GMT
Organization: University of Washington, Seattle
References: <email@example.com> <3DDBFBB5.AE995159@SpamMeSenseless.us.ibm.com>
In article <3DDBFBB5.AE995159@SpamMeSenseless.us.ibm.com>,
Phil Hobbs wrote:
>Tony Williams wrote:
>> I've measured <1uA (or <<1uA) on a variety of types,
>> at up to 15V reverse bias.
>I needed some really amazing switches for a multiplexer for a $10
>pyroelectric camera. I measured some ordinary Chicago Miniature Lamp
>red surface mount LEDS as leaking less than 100 femtoamps from -5V to
>+0.5V of bias. Together with a little illumination to provide a
>controllable 1 to 5 picoamp bias current, they worked very well. A
>description is at
>http://users.bestweb.net/~hobbs/footprints/fpspie11.pdf, and some data
>from the sensor and more discussion at http://www.pergamos.net).
>High bandgap devices really don't leak.
Agreed. I've used LEDs for some time -- possibly after hearing that
someone else (Bob Pease?) had noted their low leakage currents -- as
input protection diodes. In those circuits they were bootstrapped to
minimize capacitance, which is not all that small at nearly 0 bias.
Careful attention to reducing light (coating with something opaque)
is necessary to achieve low leakages. Perhaps others measuring LEDs
haven't been careful about light?
These leakages are significantly better than the standard low-leakage
diodes we've found.
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