SMD BJT transistor question

[Gene Pink]

Have they standardized the pinout of these things?

In reverse-engineering a cheap newfangled "smart" car battery charger that is just too damn smart for it's own good, I want to make some tweaks. Actually, I am compelled to make tweaks, you people here know what I mean. It is brand new, but it needs fixing.

So far it seems that all the transistors have the same pinout, it goes E-B-C clockwise, with C on the side by itself. Can I assume they will all be like this? It would save a lot of time if this was true, without having to look up two-digit numbers and guessing at the manufacturer to get to a datasheet for each one.

Speaking of that, if SMD parts have the same two-digit number, can it be assumed that they are at least functionally similar?

Pardon the beginner level questions, I am new to SMD. It's like a tiny three-legged flea circus on the board.

Thanks,
Gene

 

[gyraf]

No standardized pinout. Ever.

Same marking should translate to same device. Sometimes even across manufacturers.

The SMD code book (identification from the 2/3-digit marked code): http://www.marsport.org.uk/smd/mainframe.htm

Jakob E.

 

[Gene Pink]

> No standardized pinout. Ever.

Disappointing, but I was hopeful.

> Same marking should translate to same device. Sometimes even across manufacturers.

> The SMD code book (identification from the 2/3-digit marked code): http://www.marsport.org.uk/smd/mainframe.htm

This is good news.  Something positive in working with this frustratingly tiny stuff, while cleaning nose prints off of my magnifier light lens every ten minutes. Now I know why so many people here work with tubes, two dozen parts don't instantly vanish when you sneeze.

The way things are going, an SMD 12AX7 wouldn't surprise me. Sockets cost money. But that's a topic for the Brewery.

Thanks for replying, Jakob. I appreciate it.

Gene

 

[Samuel Groner]

Standard packages like SOT-323, SOT-23 and SOT-223 seem to be pretty consistent; I don't recall having seen an inconsistency amongst the manufactureres I use regularly (ON Semi, Fairchild, NXP). But that doesn't free you from the probability that there's a company out there that has managed to set its own standard...

Samuel

 

[Khron]

I'd second that opinion - all SOT23-packaged transistors i've come across so far, whether PNP or NPN, were B-C-E (if the single pin's pointing upwards, which is the collector, base is lower left, and emitter is lower right).

MOSFETS seem to follow the same rule, except for the pins being G-D-S instead of B-C-E, of course.

One larger(?) SMD database i've come across is http://chip.tomsk.ru/chip/chipdoc.nsf/vc1!readform&view=smd&cat=A&start=1&count=2000 - the "detail description" is in the english at the bottom.

The same sort of rule applies for TO220 (and bigger) packages, from what i've seen - G-D-S or B-C-E, respectively (looking at the component from the front, base/gate being on the left, center pin & tab being collector/drain, and the right-most pin the emitter/source).

Standard packages like SOT-323, SOT-23 and SOT-223 seem to be pretty consistent; I don't recall having seen an inconsistency amongst the manufactureres I use regularly (ON Semi, Fairchild, NXP). But that doesn't free you from the probability that there's a company out there that has managed to set its own standard...

Samuel

 

[PRR]

> same sort of rule applies for TO220

TO3, the Collector is soldered to the package base because that's where the heat is.

TO220, Collector soldered to the tab, for heat, and so you can bend-up a TO220 to fit a TO3 mount.

TO92, Collector soldered to internal header "flag" for heat; however there seems to be two standards for the flag (center or side) and the D-case can be molded either way?

The same "may" apply in SMD- the "biggest" or most-space pin would be Collector to throw the heat.

While "commodity" parts may follow standards, mass-production design may occasionally support an odd pinout to simplify the layout. Maybe not a batt charger, but I sure would be wary inside a cellphone.