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Author Topic: Bipolar..MOSFET..JFET..SCR..Darlington.. OMG, Transistor shopping!  (Read 638 times)
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A question that I can't seem to find a "for dummies" (aka for ME) answer for is one that a good engineer can probably tick off in seconds for the rest of us:

Skipping extreme special cases, what kind of transistors would you recommend for:

1)  Switching (low power... logic level, low current stuff)
2)  Switching (high power... motor drivers, DC loads)
3)  Amplification (microphone to Analog input, for example)
4)  Amplification ("other" sensor to Analog or digital input)

In general, I keep around some NPN "general purpose" transistors like 2n3904 or 2n2222.  For most things, they suffice and are really cheap, and can be gotten anywhere.  I know Darlingtons are essentially a cascaded transistor, making it functionally a normal transistor with really high gain.  In terms of engineering, you could classify me in the "a transistor is like a faucet" understanding level, in that I have a rough idea of the function but don't want to get bogged down in Substrate discussions.  Other than that, much of this is a mystery to me, and I suspect to many others also.

I guess the biggest biggest factors would be Price, Flexibility, and Availability... though Availability is much less an issue because of online ordering.  I'm just thinking if there's something that is around at Radio Shack that we'll overpay for, but have in hand, that's probably useful info.  Obviously there's not one "perfect" transistor, otherwise there would be only one type made.. but for Arduino-typical circuits, the range has to be considerably smaller.

Like anyone, I don't want 50 types of transistors about..  anyone have thoughts on this in a general (and "for dummies") sense?  As a hobbyist, it would be useful to know I can "get away with" two types for most cases, and buy a 50 pack of them from China for example.  In reality, this ought to be part of a larger "what basic parts should we all have" question that most learning tinkerers have..
« Last Edit: May 06, 2011, 10:22:08 am by focalist » Logged

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Quote
1)  Switching (low power... logic level, low current stuff)

General-purpose NPN transistors like 2N2222, 2N3904, or 2N4401.

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2)  Switching (high power... motor drivers, DC loads)

Logic-level N-channel MOSFET's like NDP6060L, NTD4960N, etc.

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3)  Amplification (microphone to Analog input, for example)

Rail-to-rail I/O op-amps like TLV2371/2/4, MC33202.

Quote
4)  Amplification ("other" sensor to Analog or digital input)

Same as above.

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The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons
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1)  Switching (low power... logic level, low current stuff)
Personally like some of the newer super transistors like ZTX851 (tiny e-line package, rated at 5A (20A peak) due to v. low saturation voltage!), STX724 and their complementary PNP devices.

Quote
2)  Switching (high power... motor drivers, DC loads)
Logic level N-channel MOSFET in TO220 - currently I seem to only have logic-level FETs in DPak and D2Pak forms so can't reel off a part number, but 0.01 ohm RDSon or less.  ST Microelectronics seem to have the cheapest range, narrowly followed by IRF.

For crazy performance levels I found the IRLS3036-7P (its surface mount 7 lead package but rated for logic level and is 1.5milliohm RDSon, 60V, 240A).

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3)  Amplification (microphone to Analog input, for example)
Good low noise dual opamp - used to use NE5532 and NE5534 but they might not be low-voltage

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4)  Amplification ("other" sensor to Analog or digital input)
Good low voltage rail to rail opamp - I think the ones I have are OK (LM358N) but check the specs!
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