| Electronics > Beginners |
| Darlington pairs resistors. |
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| sureshot:
Hope this is ok to ask, might seem obvious but i can't find a definitive answer to it. So i would like to try a building a darlington pair from two power transistors, they would be the TIP35C npn bipolar transistor. They will be used as a series pass element in a linear voltage regulator circuit, or zener regulator circuit. I have used single darlingtons before pnp and npn of various power ratings. As the darlington transistors have built in resistors, would i need to use them in this application of a series pass element ? I know they assist in turn off of the transistors, and prevent leakage capacitance. But i don't know if i need them for this linear application. Any help appreciated, and thank you for reading. |
| Kleinstein:
The often found build in resistors in a Darlington pair help to reduce leakage current and speed up the transistor in some applications. For a power supply it is a good idea to have at least the resistor B-E for the output transistor. This can be a rather small resistor for an TIP35, e.g. 10-100 Ohms. Usually one does not combine 2 equal size transistors, but has a smaller transistor at the input. This could be something like an BD139 (slightly on the small side) or D44H... (slightly on the large side). |
| CJay:
--- Quote from: Kleinstein on July 26, 2018, 10:45:15 am ---The often found build in resistors in a Darlington pair help to reduce leakage current and speed up the transistor in some applications. For a power supply it is a good idea to have at least the resistor B-E for the output transistor. This can be a rather small resistor for an TIP35, e.g. 10-100 Ohms. Usually one does not combine 2 equal size transistors, but has a smaller transistor at the input. This could be something like an BD139 (slightly on the small side) or D44H... (slightly on the large side). --- End quote --- Ohh, Motorola D44H01, my current (intended) go to transistor for linear PSU repairs! |
| sureshot:
This is from a TIP142 i think, are these values appropriate ? And I'm unsure on the diode, unless is protection use. Thank you for the replys. |
| sureshot:
I googled that Motorola D44H01 found nothing on it. Yes i forget things some times, yes a small drive transistor to the final power transistor. |
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