What companies make good semiconductors?

[spooney]

Looking for some replacements for a couple amps and I'm finding that there quite a few manufacturers out there that make semiconductors.Some are cheaper than a dollar a piece and some like NTE parts approach the 4 dollar range.Is there really that big of a difference in quality between these parts?Would a 1 dollar semiconductor do the same job as a 4 dollar one?is it a reliability thing?I don't have tons of cash on hand so anywhere I could save some money would be cool but if it means I'll be replacing transistors every other month i'd rather do it right the first time.can anybody maybe shed some light on this for me?

[Piercarlo]

Originally posted by spooney
Looking for some replacements for a couple amps and I'm finding that there quite a few manufacturers out there that make semiconductors.Some are cheaper than a dollar a piece and some like NTE parts approach the 4 dollar range.Is there really that big of a difference in quality between these parts?Would a 1 dollar semiconductor do the same job as a 4 dollar one?is it a reliability thing?I don't have tons of cash on hand so anywhere I could save some money would be cool but if it means I'll be replacing transistors every other month i'd rather do it right the first time.can anybody maybe shed some light on this for me?

I try to shed some (poor) light on the question. Transistors should be characterized by *process* fabrication instead of signature because the former give more information on real behaviour of devices than latter. At my knowledge, only National, in his paper databook of the early 80s has published that data... the other, generally, publish only a list of quick data which often cover simply the same devices dices packaged in different forms. I think that, whence a transistor (with same signature) is less cheap, that means (pheraps) a more specialized process of production of that devices, which hopefully has more chances to be that it declare to be as signature...
Whence more cheapest devices appear (in my opinion at least) just different marking of some general purpose process of manufacturing (generally unknows but which, usually, guarantees just typical data as hfe, FT, current and voltage limits in a rather unspecialized fashion).

If the "general process" cover also "general purpose" transistors there is not too matter of complaints. Problem arises when particular kind of devices (especially those working above 10 Amps of Ic) are sold fabricated not with their original process but with someone more "tricky" which nominally meet the gross perfomance of original part but don't meet the fine requirements (and this it's devisable when for these "equivalents" are just provided the quick data *but not* curve data which instead reveal these devices as totally different devices from those they claim to be in signature).

My criterion, in choice of critical devices, is to rely only on companies that provided full specification with curves and discard those which delivers only quick data because, in the latter case, the probability of having to face only with general unspecialized devices (more or less opportunistically marked to satisfy "market demands") is very high.

In general: the choice of the source of semiconductor devices must be done keeping in mind the final use. If critical you must rely only on "serious" manufacturers which provided (with some added cost obviously) full data and curve specification. If uncritical instead you may accept some risk and buy devices with unqualified behaviour except for their maximum limits, which don't tell much more of this: just maximum limits.

Ciao
Piercarlo

[lineup]

NTE is too expensive - if an alternative can be found
... and usually you can find them

There are many good semiconductor manufacturers.
Most of them are!

The only thing to look up for is faked copies.
Just like jeans can use a faked brand, to 'ride on' the reputation of quality fabrication.
A very low price can be one indication for such bad stuff.

But on the other hand,
there are distributors, suppliers of low price good stuff,
that is made by, compared to western standard, low paid workers
in Taiwan, China and Korea and similar countries.

If you stick to some dealer with a trusted name,
and mostly these are rather big companies, with stores worldwide,
you should be rather safe even if prices are low.

Farnell, Maplin ... what more do we have?


In each and every country is most often one leading supplier.
Especially in smaller countries.
This makes the choice of semiconductor dealer very easy
as this is just about the only alternative
- with a wide and covering range of electronics components.


Buying in internet shops from those big chains
is probably what DIY builders mostly do.
You can have your stuff within 7 days.


lineup

[spooney]

so is mouser a reliable retailer?or maybe parts express?

[Damon Hill]

I'd go with Digikey or Mouser, and OnSemi (the spun-off semiconductor manufacturing division of Motorola) for power transistors. Sanken and Toshiba are also good semiconductor manufacturers, but harder for me to obtain. I'm generally not familiar with power MOSFETs, so I can't make any useful recommendations there.

After that, you need to determine your specific requirements (voltage, current, power, number of devices, etc) to make selection from the available range of devices.

Sources like NTE tend to be at least twice as expensive, and I'm less confident of reliably specifying parts from them. Counterfeited semiconductors are notorious for certain part numbers and will almost always let you down for reliability. The sources I mention at the top should be very reliable suppliers of genuine parts.

Do you have specific parts numbers you could name? We might be able to recommend substitutes.

[TomWaits]

Originally posted by spooney
so is mouser a reliable retailer?or maybe parts express?

I found Digikey to have great service and faster shipping and that is important when shipping across the border to Canada but perhaps not a concern for you. I think you would be safe buying your components from any "franchised" distributor. Happy spending!

Shawn.

[spooney]

Specifically I'm looking for these or an equivalent : 2N6491,2N6488,LM337T, and KTD998

[Damon Hill]

The LM337T is a negative voltage regulator, a power integrated circuit rather than a transistor. It's in a TO-220 plastic package, and either Digikey or Mouser will be a reliable source. Digikey also stocks the 2N6491 and -6488 at what look like very modest prices.

A data sheet for a KTD998 is here:

http://www.icstock.com.cn/DATASHEET/KTD998.PDF

I've never heard of this manufacturer; does this look like your part? The NTE part may be as good a choice as many.

[TomWaits]

Originally posted by Damon Hill
A data sheet for a KTD998 is here:

http://www.icstock.com.cn/DATASHEET/KTD998.PDF

I've never heard of this manufacturer; does this look like your part? The NTE part may be as good a choice as many.

Nor I, what heck is tripple diffused all about? Without looking to close, I'd find an On Semi equivalent and then you'd get all of your components from one disti and one shipping rate. But then again the KEC may be special to you they are HERE

Cheers,

Shawn.

[alfiax]

ktd998 looks like a 2sd998 equivalent.

edit: oddly enough there seem to be multiple forms of this transistor out there. I bet the one on the right in this link is the one you need.