Transistor for fan mod, does it matter which one?
03-25-2009, 01:51 AM
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Transistor for fan mod, does it matter which one?
The transistor in the fan mod "kit" is a PN2222AD26ZCT-ND but this one seems to have the same specs. Furthermore, Q4, which is mentioned in the alternate suggestion in the "how to" thread is a whole different part number altogether. I'd rather use the circuit as designed in the proto area, would the Radio Shack one work there or will Q4 work, or does it even matter?
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03-25-2009, 07:52 AM
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Boost Pope
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Yes, the MPS2222A and the PN2222A are essentially the same device. Here are the datasheets for them:
MPS2222A
PN2222A
You can see that they have the same pin configuration, and all of the operational specs are virtually identical. When you see two devices with the same "root" number, in this case 2222A, it's a good bet that they're pretty much the same part from two different manufacturers. This happens a whole lot with discretes.
Q4, the ZTX450, has a few minor differences, but basically it's just rated for slightly higher power dissipation than the other two (1W, vs 625mW).
So yes, any of them will work.
Provided you don't exceed any of the ratings, pretty much all NPN transistors are freely interchangeable in simple switching applications. You could stick a 2n3055 in there and it'd work. Were we building audio amplifiers, then we'd care more about internal capacitance, gain, and so on. But in this application it doesn't matter in the least.
MPS2222A
PN2222A
You can see that they have the same pin configuration, and all of the operational specs are virtually identical. When you see two devices with the same "root" number, in this case 2222A, it's a good bet that they're pretty much the same part from two different manufacturers. This happens a whole lot with discretes.
Q4, the ZTX450, has a few minor differences, but basically it's just rated for slightly higher power dissipation than the other two (1W, vs 625mW).
So yes, any of them will work.
Provided you don't exceed any of the ratings, pretty much all NPN transistors are freely interchangeable in simple switching applications. You could stick a 2n3055 in there and it'd work. Were we building audio amplifiers, then we'd care more about internal capacitance, gain, and so on. But in this application it doesn't matter in the least.
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03-25-2009, 02:12 PM
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Yeah, I concluded that the radio shack and the digikey one in the kit were pretty much the same by googling the part numbers and looking at the datasheets, I just don't know anything about transistors, so I didn't know if there were any hidden differences.
Thanks, Joe.
Thanks, Joe.
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03-25-2009, 02:24 PM
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Boost Pope
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Nah, those two are pretty much ripoffs of one another. Like I said, the ZTX (Q4) is a fairly different part, and it'd matter if we were using it in a linear application, or at a high frequency, or we cared about the saturation points, or whatever. But as a simple low-current switch, pretty much any NPN device in the world will work in that spot.
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