Transistor datasheet symbol.

[Diabolical Artificer]

I've been looking for a more easily obtainable replacement for a power transistor 2SD1017. It is a replacement for one that burnt out in an electronic ignition on a vintage bike; I hope the mods will allow this to stand.

From the usual searches on line there are various equivalents one of which is the D1017's larger brother the D1018. However I encountered a symbol I've not come across on the D1017 datasheet which looks like a beta symbol. It says " ultra high "B" transistor ". Switching time? See PDF.

Thanks for looking, Andy.

[paulsherwin]

'Beta' is another (somewhat obsolete) term for hfe. 500 min is certainly very high gain for a power transistor.

[G6Tanuki]

It's a Darlington/Super-Alpha 'transistor' so 500 is quite a believable hfe/beta.

[paulsherwin]

Ah, didn't notice it was a Darlington.

[Diabolical Artificer]

Thanks for the clarification. a 2SD1018 as well as others is recommended as a replacement on the alltransistor site, but Miguel our friend in Cuba says this is not suitable to replace it. as, as you say it has a high hFE of 500.

In this transistor is there actually two transistors in a Darlington configuration on one chip or an equivalent device printed on a chip and does it matter?? In the datasheets how important are the equivalent emitter resistors and other equivalent discreet components like the zener. Still a bit unsure how to interpret some aspects of datasheets.

Can anyone think of a suitable replacement? A 2SD799 is recommended on one hit I got when searching which has a possible hFE of 600, as long as its not drawing too much current, I think, if I've interpreted the datasheet correctly.

Thanks for your help,Andy.

[G6Tanuki]

"Darlington" or super-alpha transistors can be implemented as separate devices, or integrated on one slab of silicon.

The single-slab-of-silicon types are generally better because the two transistors share the same thermal environment. There are plenty of Darlingtons that fit your need - it's not as if it needs much high-frequency capacity.

[orbanp1]

Hi Dr Wobble,

The 2SD1017 is a 250V 2A NPN "regular" (non darlington) power transistor. The datasheet you gave is on the 2SD1071, which is indeed a darlington transistor, and is not the one you had in your equipment.
A suitable replacement could be any 500V 5A NPN transistor which are widely available, and has ample safety margin for your application. Just plug the parameters into your favorite outlet's search engine.
At Farnell the cheapest is the NXP BUJ303AX: http://uk.farnell.com/nxp/buj303ax/t...20f/dp/1972411

Good luck, Peter

[paulsherwin]

Well spotted Peter. I wondered what a Darlington transistor was doing in a motorcycle electronic ignition system

[lesmw0sec]

Originally Posted by paulsherwin

'Beta' is another (somewhat obsolete) term for hfe. 500 min is certainly very high gain for a power transistor.

I seem to recall that even earlier, it was alpha' as opposed to alpha (small signal/large signal?) Can't remember!

Les.

[Herald1360]

Alpha is the current gain in common base mode. With modern devices (as opposed to point contact types) it's always less than 1.

β=1/(1-α)

Point contact devices don't work very well in common emitter mode......

Hfe is small signal current gain

HFE is DC figure

[jim_jobe]

And alpha dash was common emitter gain.

[Diabolical Artificer]

Well spotted Peter, sorry to lead everyone up the wrong path. However your replies have clarified the point about the beta symbol. That as well as other ways of expressing gain on data sheets.

I found a BUF644 in my transistor pull box which is a HV SWOT -simple switch off transistor, as well as several HV pulls from TV's, that I thought might do as a replacement at first but have now ordered something closer to the original as I don't want to damage the new ignition coil.


I've replaced two ignition coils now, weather the burnt out D1017 caused the original problem I'm uncertain. I've yet to properly examine the PCB from the ignition unit.

Thanks again for your help,Andy.