What, if any are the electrical differences between transistors in T018 or TO92? - Page 1
Forum section: electronics / beginners

author: commie
author_rank: Frequent Contributor
timestamp: June 20, 2015, 08:54:25 pm
content: Hi folks,I was just wandering if there are any electrical differences between the expensive T018 and the cheaper T092 packages for the same transistor?Examples are 2N2222A(T018) or P2N2222A(T092), I tend to think t018's are better quality but what do you think?CheersCommie

author: c4757p
author_rank: Super Contributor
timestamp: June 20, 2015, 08:59:50 pm
content: Nope, practically there is no difference. The quality certainly isn't higher - the packaging can be better for one and only one reason, the hermetic seal canvery, very slightlyincrease reliability particularly in harsh environments, hence their use in military applications. The transistor die inside is exactly the same.

author: Ian.M
author_rank: Super Contributor
timestamp: June 20, 2015, 09:11:54 pm
content: There may however be a difference in the maximum permitted power dissipation and thermal resistance to ambient. Check specific datasheets for details.

author: commie
author_rank: Frequent Contributor
timestamp: June 20, 2015, 09:21:52 pm
content: Quote from: Ian.M on June 20, 2015, 09:11:54 pmYeah, I gathered that, I was pointing more to bandwidth product.I'll tell you what though, there are big differences between different manufactures of the same part, for example I find Moto/On to be the best you can get.Thanks for the replies.CheersCommie

author: TimFox
author_rank: Super Contributor
timestamp: June 20, 2015, 10:03:59 pm
content: When you go up to TO-5 or TO-39, there are very nice heatsinks that surround the metal package under spring tension to improve power capability. Heat sinking is not so efficient with TO-92.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 20, 2015, 11:48:36 pm
content: I wouldn't say reliability or other features of metal case parts is poor (in terms of advantage). Though I don't know by how much that actually matters. So, I don't have the numbers, or even the test methodology to establish that; I would just suspect they have at least some reason besides inertia.The main direct / advertised difference is TJ going up to 175 or 200C, which is, at best, only rarely available in plastic packaged parts.But yeah, if you aren't doing high temperature, mil spec, down hole, etc. stuff, you'll likely never see the difference; plastic case parts are amazingly reliable.You'll see package differences on the highest speed parts (fT > a few gigs), but that's about parasitics. The die, in and of itself, will be perfectly identical across parts of a given type but different package.Tim

author: dacman
author_rank: Frequent Contributor
timestamp: June 21, 2015, 02:02:34 am
content: For the TO-18 2N2222A, the collector is tied to the (metal) case (just look at the bottom of one). The collector is where the major voltage drop occurs, and therefore where most of the power is dissipated. Also, I can put a heatsink on the TO-18 (P/N 322400B00000G, which is available from suppliers such as Newark and Mouser). Even though that heatsink will also fit on a TO-92, it would not be nearly as effective as on a TO-18. (I use that heatsink on both the TO-71 and TO-78 also.)

author: SeanB
author_rank: Super Contributor
timestamp: June 21, 2015, 07:33:23 am
content: Basically no difference, but there are edge cases where the one package is better than the other. Plastic package is lower cost, slightly lower capacitance and inductance ( but really only going to matter at a frequency where the die inside is no longer going to be acting like a transistor with any gain) and able to dissipate lower power. Metal is better for high power use, as it has the ability to be heatsinked easily with a good thermal path to the die. I have soldered them to a copper tag for use where I needed a small heatsink and did not have a clip on one around. Metal case is good for use as a temperature sensor as well, using the die as an amplified diode.

author: Simon
author_rank: Unknown
timestamp: June 21, 2015, 12:54:30 pm
content: I think the main reason is the metal can will dissipate more. I have always noticed a stark difference in current capability (x3) between plastic and metal.