Recent content by bobosoft

Here is the spec: http://www.formfactors.org/developer%5Cspecs%5C4_Wire_PWM_Spec.pdf You are right about it being open, not 5v, Intel says it has to be pulled up in the fan. "This signal must be pulled up to a maximum of 5.25V within the fan." the 2SD1273 is not darlington but it...

That's not quite how a bipolar transistor works. The current flowing from the base to the emitter determines the amount of current that can flow from the collector to the emitter. That proportion is called the gain so if you had 1ma through BE and a gain of 1000 (as is typical of darlington) you...

Id rather not argue about it, my concern was preventing frustration on the part people trying to implement your circuit who might think they had done something wrong.

Oh man, where do I start. Doing all of the math required to predict that circuit would make my head hurt. What I can tell you is that it is not what you wanted and the only reason it works at all for you is because you are using a TIP120 which is a darlington transistor which is an integrated...