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Old 10th January 2004, 04:01 AM   #1
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Default Whats the purpose of this transistor?

In this article it contains the following schematic, I understand what most everything is doing except that transistor in the middle.
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Old 10th January 2004, 04:10 AM   #2
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with not even looking at the article or looking at the circuit that close...LOL....shoot me!!!...its a basic switch for the comparator.....so disregard what I just posted

DIRT®
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Old 10th January 2004, 05:05 AM   #3
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It adds an offset ("85 mV Deadband") between the 2 comparators (pins 5 and 6) since the voltage at pin6 is given by

Vpin6 = Vpin5 + Vbe * (10k / 62k), with Vbe = 0.6
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Old 10th January 2004, 09:31 PM   #4
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Oops, the offset should be:

Vpin6 = Vpin5 + Vbe * 10k / (10k + 62k), with Vbe = 0.6

brad
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Old 18th January 2004, 02:42 AM   #5
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Also for this circuit instead of the Crystal digipots, could I use Maxim DS1802's which have the pushbutton control? I happen to have two 1802's allready so that would be easier to use.
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