Transistor with quite high hFE?  - Page 1
Forum section: electronics / beginners

author: BravoV
author_rank: Super Contributor
timestamp: February 04, 2013, 03:54:28 am
content: While ago a friend gave me a handful of unused old Japanese transistors with part no 2SD1273, he did mention that these are old stuff but powerful transistors and didn't say any details what he meant by that.Its been a while and never really paid attention to it, and just today when tidying up my components bins, on curiosity I downloaded the datasheet to check it out, and I was amazed at how high the hFE of this transistor. The pdf of the datasheet ->HereIs this normal to have such a high hFE for this kind of transistor ? May be its just me (just a hobbyist), I've never seen such high beta with such relatively high current capability. At chart above, even at 2 Amp, the hFE still at about 400.Just curious what kind of circuit can be used for this high hFE advantage ?

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 04, 2013, 04:02:43 am
content: most power darlingtons are within the 5K hFe. here's the TIP125 PNP i randomly dig from my archive.

author: BravoV
author_rank: Super Contributor
timestamp: February 04, 2013, 04:10:57 am
content: Quote from: Mechatrommer on February 04, 2013, 04:02:43 amI thought darlington has quite high Vce sat ? Look at the chart, the Vce sat is quite low, but not sure, the datasheet doesn't mention its a darlington.From the characteristic, is it a darlington ? Check the datasheet please.

author: Marco
author_rank: Super Contributor
timestamp: February 04, 2013, 04:22:26 am
content: I assume it's a super beta transistor, although with a pretty high max Vce.

author: sorin
author_rank: Frequent Contributor
timestamp: February 04, 2013, 06:20:18 am
content: Quote from: BravoV on February 04, 2013, 04:10:57 amIts not a darlington.

author: BravoV
author_rank: Super Contributor
timestamp: February 04, 2013, 07:06:39 am
content: Quote from: Marco on February 04, 2013, 04:22:26 amOk, super beta it is, but what do you mean by high Vce ? Please elaborate further.@Sorin : Thanks.

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 04, 2013, 11:50:52 am
content: this is the Vce saturation chart for the TIP125. "high" is a relative term, so YMMV.it doesnt have the Transition F-I plot though, its 300pF output capacitance so i believe the TIP125 is quite a slow bjt.and then, "slow" is another relative term, so YMMV.

author: BravoV
author_rank: Super Contributor
timestamp: February 04, 2013, 01:48:01 pm
content: Quote from: Mechatrommer on February 04, 2013, 11:50:52 amCmiiw, you sound like you keep insisting its a darlington ? What is the criteria if its or not ? Just because it has high beta ?Sorry Mecha, although I'm not qualified at all to discuss this matter, let alone argue about it, its just you sound not very convincing.

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 04, 2013, 02:15:39 pm
content: no i'm just providing the data for darlington transistor since 1) you asked if 1000 hFe is normal? 2) you claimed the darlington "should" has high Vce? from the graph they are about the same. but if your intention is to rule out darlington transistor, sorry i've misinterpreted this thread, i havent checked the datasheet that you have and will be happily delete all my post. cheers

author: SeanB
author_rank: Super Contributor
timestamp: February 04, 2013, 03:27:06 pm
content: Try looking at this transistor....STC03DE170HVThat is one complex device there.

author: jimmc
author_rank: Frequent Contributor
timestamp: February 04, 2013, 07:29:33 pm
content: Think of a darlington transistor as a composite device made of two discrete devices.The VCEsatof the composite device is equal to the VBEof the output device plus the VCEsatof the driver.(note that the output device is not necessarily saturated)For a silicon device this means that its VCEsatwill be greater than 500mV even at relatively low currents.(and at room temperature)Since VCEsatof the 2SD1273 is well below 100mV at 100mA it cannot be a darlington.For comparison the (darlington) TIP125 has a VCEsatof 0.7V at the same current.Jim

author: codeboy2k
author_rank: Super Contributor
timestamp: February 05, 2013, 02:40:03 am
content: It's not very fast, the transition frequency falls off at higher currents, so it might make a suitable audio output driver.Mate it with its complement in a push pull, you could probably make a 20W or 30W amplifier from it.

author: codeboy2k
author_rank: Super Contributor
timestamp: February 05, 2013, 03:28:58 am
content: Quote from: SeanB on February 04, 2013, 03:27:06 pmcool. Never seen that before. Since I don't do either 3-phase stuff or off-line SMPS at all, I've never come across it.It's not really that complex as it seems at first glance, but the tech is cool. It's an N channel MOSFET in the collector-emitter region of a NPN BJT... I can almost see how this would be constructed on the substrate... put a gate oxide across the P region (the base) that separates the two N wells of the collector and emitter, and you have an N-channel enhancement mode FET that can be kickstarted with a high-current base pulse and held with a low-current gate voltage. way cool!The benefit is higher switching speeds of the MOSFET and lower conduction losses of the BJT. You no longer need the high base current to keep the BJT in saturation, but only the gate voltage, which has little to no current requirements.here's the appnote:http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/APPLICATION_NOTE/CD00149906.pdf

author: BravoV
author_rank: Super Contributor
timestamp: February 05, 2013, 05:16:44 am
content: Quote from: jimmc on February 04, 2013, 07:29:33 pmNow thats a proper and much-much better explanation, thanks a lot Jim.Quote from: codeboy2k on February 05, 2013, 02:40:03 amOk, what is so special about this so called "super beta" transistor (is this the correct term ?) good for ?Just for audio amplifier ?

author: boB
author_rank: Frequent Contributor
timestamp: February 05, 2013, 08:53:19 am
content: Quote from: codeboy2k on February 05, 2013, 03:28:58 amLooking at this part immediately reminded me of this GaN Cascode article I saw recently...http://electronicdesign.com/power/cascode-configured-gan-switch-enables-faster-switching-frequencies-and-lower-lossesboBEverett, Wa

author: codeboy2k
author_rank: Super Contributor
timestamp: February 05, 2013, 09:52:02 am
content: Quote from: boB on February 05, 2013, 08:53:19 amNice read , I hadn't seen it. Thanks for the link, Bob and welcome to the forumCheers!