Re: how to control LED array? (follow-up)
- From: John Fields <jfields@xxxxxxxxxxxxxxxxxxxxx>
- Date: Sun, 29 May 2005 13:02:18 -0500
On Sun, 29 May 2005 16:23:54 GMT, Rich Grise <richgrise@xxxxxxxxxxx>
wrote:
>On Sat, 28 May 2005 18:32:43 -0500, John Fields wrote:
>
>> On Sat, 28 May 2005 15:19:58 -0500, John Fields
>> <jfields@xxxxxxxxxxxxxxxxxxxxx> wrote:
>>
>>
>>>With a collector current of about 300mA, Fairchild spec's Vce(sat) at
>>>about 0.2V for a 2N4401, so the multiplexed transistors will be
>>>dissipating:
>>>
>>> (Vcc - Vce) Ic 4.8V * 0.24A
>>> P = ---------------- = -------------- = 0.144 watts
>>> 8 8
>>>
>>>Which the 2N4401s can easily handle.
>>
>> ---
>> Aarghhh!!! It should be:
>>
>>
>> Vce(sat) Ic 0.2V * 0.24A
>> P = ------------- = -------------- = 0.006 watt
>> 8 8
>> ---
>
>John, have you ever considered making these corrections _before_ you
>hit send?
---
I did...
--
John Fields
Professional Circuit Designer
.
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