Re: TI-H: LED Backlight

To: ti-hardware@lists.ticalc.org
Subject: Re: TI-H: LED Backlight
From: Grant Stockly <gussie@alaska.net>
Date: Thu, 28 Jan 1999 15:54:33 -0900
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In-Reply-To: <002901be4ad5$913c7320$c9648ed1@vizzini.rdtech.>
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>From: Grant Stockly <gussie@alaska.net>
>>>In the meantime, if anyone wants to use the current version [of
>>>the autoswitch] it will work just fine if the first stage of the output
>>>is replaced with a darlington
>>
>>A 2N2222 will work fine.  It shouldn't use over 100ma.
>
>
>It would work fine if transistors came with less variation in the
>beta, however, that circuit is very sensitive to transistor beta,
>not all transistors will work well, I'm estimating about 20% or
>so (based on a sample of about 25) have high enough beta to
>work in that circuit.  A darlington will work better, and the price
>difference is negligible.

The calc isn't going to switch the line any faster than 10MHz.

References:

Re: TI-H: LED Backlight

From: "David Knaack" <dknaack@geocities.com>