Differences in transistors

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qdgjcl
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Differences in transistors

Post by qdgjcl » Tue Mar 18, 2003 11:38 am

Is there a difference between, MPS3904 and 2N3904 transistors?<p>Brad

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haklesup
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Re: Differences in transistors

Post by haklesup » Tue Mar 18, 2003 5:07 pm

I believe they are. Both part numbers cross reference to the same NTE rfeplacement part number www.nteinc.com/specs/100to199/pdf/nte123ap.pdf<p>the 2N prefix is a standard from JEDEC and is much more common http://www.chipdocs.com/pnsearch/search ... 732&ReR=GG but the MPS is a prefix from Motorola (I think MJ or MJE is a more common prefix from them now) see http://support.tandy.com/support_suppli ... /31362.htm or here http://www.chipdocs.com/pndecoder/datas ... S3904.html

chessman
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Re: Differences in transistors

Post by chessman » Tue Mar 18, 2003 7:05 pm

But since they're differenct manufacturers won't there be small, minute device differences?

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Edd
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Re: Differences in transistors

Post by Edd » Wed Mar 19, 2003 10:31 am

Brad:
Seems like the 3904 /3906 series were originally parent devices of Fairchild Semiconductor. Very popular GP xstr units and initially qualified and released under the JDEC series of 2N prefixes . And then, as usual, Motorola comes along and second sources as a MPS series. Usually this works as a spin off of some highly developed semiconductor that is of Mil/Aerospace quality and reliability and typically metal encased and even into the radiation resistant category (Look out Saddam !) and it may be downgraded on some specs and come out in a plastic casing. Seems like Semelab is the only
sourcing of these devices in the metal TO-18 housing nowadays. Plus Fairchild seemed to like their round ceramic housings.
On device selection parameters one is probably firstly interested in device polarity (npn/pnp?) then the voltage breakdown specs and then the units current/power capability and then the Beta/gain of the unit .Being of a general purpose
variety its alpha or hi freq specs are probably not of too much importance unless its to be incorporated in a fast switching mode of implementation.
Probably the most important one thing you need to confirm is if there has been no variation in the case’s lead configuration such that the BCE lead arrangement is instead CBE…..that does mess things up.<p>73's de Edd
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haklesup
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Re: Differences in transistors

Post by haklesup » Wed Mar 19, 2003 10:34 am

Even within the same manufacturer, lot to lot differences exist. This is why it can be a challenge to build a differential amplifier out of discrete components. People pay a premium for matched pairs of transistors or even pairs mounted in the same package.<p>Look at the Electrical Characteristics of the datasheet. All of the parameters are listed as a min/typ/max value. Some of the parameters vary a great deal. Good design practice focuses on the least sensitive parameters for calculations and avoids designs that depend on a particular variable being predictable.<p>Sometimes the differnnce in part numbers is simply how tight the range of some of these parameters are but otherwise the part is the same.(especailly military grades)

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Re: Differences in transistors

Post by analogee » Wed Mar 19, 2003 9:58 pm

An interesting question. I used to be under the impression that the MPS series devices tended to be better than generic 2N devices. Any device, by the way, that starts with "2N" is JEDEC registered - basically a group of manufacturers have agreed on a series of specs that the device must meet. This does not absolutely guarantee perfect compatibility between the same numbered devices between 2 manufacturers, but in practice, it pretty much makes them interchangeable. I've never been bitten by taking this viewpoint.<p>Anyway, the only real way to answer this is to actually check datasheets. That's your job, Brad, if you want to use one of these devices. But, heck, I got curious, so I went to On Semiconductor's website (old Motorola discretes are now made by On - [url=http://www.onsemi.com)]www.onsemi.com)[/url] and laid the 2 datasheets side by side on my computer desktop.<p>To my surprise, the MPS device was the same, or WORSE, on every spec that I surveyed. Most significant differences:<p>IC (continuous): MPS - 100 mA; 2N - 200 mA
storage time: MPS - 900 ns; 2N - 200 ns<p>Wow! switching time is dramatically slower on the MPS device. I have to figure that On is selling the MPS devices to people who don't care about switching speed. They may just have a bin where they throw the dogs, and label these MPS3904.<p>The collector current difference is also rather surprising, almost to the point where I wonder if it is a misprint. Both devices are in the same package.<p>Anyway, given all that, the MPS3904 should be a cheaper device. In practice, 3904's are so cheap to begin with, I'd never bother with the MPS3904 unless I needed some junk transistors for a project and had some laying in my junk box, or I was designing something for production in the 100,000's or more.<p>Regards,
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Re: Differences in transistors

Post by rshayes » Fri Mar 21, 2003 6:57 am

I believe that the 2N3904 and 2N3906 were some of the earliest Motorola transistors in plastic packages (TO-92). This would have been about 1967, when plastic transistors were just being put on the market. The plastic transistors made by Fairchild were in packages with ceramic bases and plastic encapsulation, rather than the molded plastic package. This probably put them at a cost disadvantage. I believe that Texas Instruments was offering the 2N3711 in a TO-92 package in 1966. General Electric also had a few transistors available in a slightly different plastic package from the TO-92. The registrations for these devices all specified plastic packages.<p>Later, Motorola began putting well established types, such as the 2N2222, in plastic packages. These could not be labeled as 2N2222, since the registration specified the metal TO-18 can. These were labeled MPS2222. Other non-registered devices were also offered using the MPS prefix, such as the MPSU04 and MPSH10 and some devices with MPS6000 numbers.<p>The MPS3904 and MPS3906 appear to be devices with looser specifications. This may just indicate less rigorous testing, or the omission of some tests, leading to a lower cost if you are buying a few hundred thousand or so.

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Re: Differences in transistors

Post by chessman » Fri Mar 21, 2003 2:06 pm

Didn't know TI used to make transistors....kinda makes sense cause all those gates had to come from transistors in the first place :)

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