Re: TI-H: LED Backlight
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Re: TI-H: LED Backlight
From: Grant Stockly <gussie@alaska.net>
>>>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.
Huh? Perhaps you misunderstand me. The problem is not
the switching speed, it is the gain. In the circuit as it appears
on my web page the gain of the transistor must be fairly high,
something more than 200 for the NPN's I was using, otherwise
the final output transistor will not allow enough current for the
inverter to turn on (typically around 5-12mA, minimum acceptable
is about 20mA).
DK
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