Diotec Semiconductor or Central Semiconductor

[Agentfoot]

I need some MPSA56 transistors. I usually use Onsemi products but these are my only two options.
Are these brands considered quality brands?
The price difference between the two is big. Diotec is $0.22 USD and Central is $0.77 USD.

[Whales]

The MPSA56 looks like a jellybean ~0.5W ~0.25A 80V PNP transistor.  That's a lot of money for one of those, I usually pay a few cents for similar specced parts.

> Are these brands considered quality brands?

What are you needs regarding quality?  Product lifetime numbers?  Temperature numbers? 

Most cheap transistors are very reliable.  The datasheets are quite honest.  As long as I use a transistor in spec I generally have not felt a need to worry about anything further.

Diotec and Cental look to be European companies.  Is that a requirement for you?  I wonder if they actually make the silicon themselves or buy it from elsewhere and repackage it.


Also: are you after TO-92 with a very specific pinout (every permutation seems to be done in TO-92), or is SMD fine?

[al777]

My stock of BC549/559 and 2N7000 is from Diotec. Never had any issues with them. Not commercial projects though, your requirements may be very different. COO is China.

Central Semiconductor is known to me as a "second-source" parts manufacturer, i.e. they often manufacture parts that went obsolete on the OEM side (like OnSemi's MPSA56), maybe they even acquire licenses from OEMs, hence their price is closer to the original.

Digikey has OnSemi's BC640 in stock @ ~$0.6USD https://www.digikey.ca/en/products/detail/onsemi/BC640TA/3042485 - check, maybe be a good substitute (2x max Ic vs. MPSA56, if I saw correctly)?

[edavid]

Arrow has the Diotec parts for $0.0117 + tariff and the Central Semi parts for $0.24

https://www.arrow.com/en/products/mpsa56bk/diotec-semiconductor-ag

https://www.arrow.com/en/products/mpsa56-pbfree/central-semiconductor

[David Hess]

Central Semiconductor takes over production of obsolete parts.  They tend to be the most expensive option, and I do not know why  someone would buy 2N3904s and 2N4401s from them.

I do not have any complaints about Diotec Semiconductor.  I have switched to using them as National, Fairchild, and On Semiconductor have discontinued their small signal parts, so they are my default now.  I wish they would make high power and high frequency medium power parts.

[Agentfoot]

Thank you everyone for your replies. I just ordered the Diotec ones. I just wanted something that would last another 26 years like the original.

Guess I was just over thinking since I am use to people being very picky over capacitor brands.

[Whales]

Usually transistors fail as victims, not causes, of problems.  Too high of current, voltage (including ESD) or temperature.   Their silicon die area is so small, thin and delicate that they tend to blow up before anything else, acting like a very fast fuse.  Something else in your circuit might have changed to cause your transistor to blow and might also kill your replacement.

Sometimes transistors can directly fail, however.  Their hermetically sealed plastic casings can break and let moisture in.  Bondwires can break.  They can suffer electro-chemical changes from long operation (more common in smaller transistors like you find in ICs, but still theoretically possible in bigger transistors like these too).  All of these self-failure modes should take magnitudes longer than (eg) electrolytic capacitor failure, but I don't have any actual data to back that up.


At a minimum it might be worth holding your finger against the replacement transistor whilst its running to see if it gets too hot (if you can't hold your finger on it due to pain then it's too hot), assuming it's not connected to dangerous voltages or the like.  Ideally you would also probe its voltages with a multimeter or a scope to confirm it is operating in safe conditions, and have a full understanding of its circuit, but that's not an easy ask.

Good luck, hope the repair goes well 

[temperance]

If it is for audio, BC639/640 are excellent low noise transistors. But the pin order is different.

[Agentfoot]

Usually transistors fail as victims, not causes, of problems.

This explains it well. Makes total sense. I was definitely over thinking it.

My MPSA56 is just getting replaced for good measure. It was being used to drive a 2N6491in an old car audio amplifier. The 2N6491 shorted collector to emitter. Also had a MPSA06 driver on the other channel shorted collector to emitter. It drives a 2N6488. My guess is someone was running the amp into clipping or ran it at the wrong impedance, but I am not an expert.

[Agentfoot]

If it is for audio, BC639/640 are excellent low noise transistors. But the pin order is different.

Thanks I will keep these in mind for next time. It was being used to drive the outputs in a car audio amplifier.

[Agentfoot]

Pictures for anyone interested. It is a 300W Precision Power, Power Class amp made in 2000.