User:Jstapko/EngLab.2N2222

This page is to document my search for the differences between the 2N2222 and 2N2222A

My original Google search was "2N2222 vs 2N2222a," on April 07, 2014

The first result was http://forum.arduino.cc/index.php/topic,11276.0.html. This hints that the difference lies in Vebo, Vcbo, and Vceo. It provides an additional link to the Transistor Museum: http://semiconductormuseum.com/Transistors/Motorola/Haenichen/Haenichen_Index.htm This is an extensive history of the development of the 2N2222 as told by Jack Haenichen, its inventor at Motorola in the 60's. This provides great details on technical details such as the annular ring process, STAR geometry and some example circuits. This website facilitates access to even more detailed information on these processes by listing Jack Haenichen's patents, which can be read online with one of several sites such as pat2pdf. However, I did not find any actual datasheets or links to such at the transistor museum, so I returned to my original results and clicked link 2, the Wikipedia page on the 2N2222. This says that "PN" prefixed to the part number means that it is a plastic, TO-92 package, and has less allowable maximum collector current. Wikipedia provides links to 2 datasheets, one for a Fairchild PN2222 and another for a STMicro 2N2222A. Examining these datasheets shows that the 2222A indeed has higher voltage ratings, but it is unclear from this whether the difference is due to one being an "A" and the other being a non-suffix, or if it is due to the ST micro being in a metal package and the Fairchild being in a plastic package. Afte4r perusing the datasheets aond comparing with the arduino forum post, I returned to the original results and clicked link 3: http://homemadecircuitsandschematics.blogspot.com/2012/02/how-to-understand-transistor-2n2222.html This page generally supports the theory that the major differences are in the breakdown voltages mentioned above, but suggests that there are other subtle differences such as transition frequency (250MHz for the 2222, 300MHz for the 2222A) and the " base optimal trigger voltage." this website also provides a link to a Phillips datasheet for both devices, which allows side by side comparison of both devices from the same manufacturer/time: http://pdf1.alldatasheet.com/datasheet-pdf/view/15068/PHILIPS/2N2222A.html This datasheet supports the claims of link 3, which was probably pretty much copied from the datasheet. I then returned to the search results and checked result 4 (not counting the images): http://www.electronicspoint.com/quick-stupid-question-difference-between-2n222-and-2n222a-transistors-t10816.html. This website provides a link to a different source for a Phillips datasheet identical to the one above. The discussion also seems to say that a 2N2222 will ALWAYS be in a metal case. Toward the end, comments suggest that some datasheets break this rule, and are inconsistent with the standard (what standard?) and can use 2N2222 to describe a plastic packaged device.

Other search results to explore include:
 * http://www.pci-card.com/2n2222a.pdf
 * http://www.next.gr/components-datasheets/2N2222.pdf
 * http://alltransistors.com/transistor.php?transistor=1774
 * http://www.utdallas.edu/~yxc101000/courses/3111Lab/handouts/2N2222.pdf

Initial checking shows that all of these are datasheets, and some include both devices in a single sheet)