what does the second part of the transistor code stand for?

I have a 2n2222 a331 and a 2n3904 h331 and s8050 d331

What do the a331, h331 and d331 stand for?

I put "2n2222 a331" into my favorite search engine to find out.

Lot or date code, exact format depends on the manufacturer and is described (often very briefly) in the datasheet.

It could be a date code or a factory code, etc. You’d have to find the datasheet from the particular manufacturer and it MIGHT tell you.

When I Googled 2N2222, the 1st thing I found was the [u]datasheet[/u] for an On Semiconductor PN2222A and it does explain the markings.

Idahowalker:
I put "2n2222 a331" into my favorite search engine to find out.

Well, I did too could not find it. Maybe you give it a try too?

I do happen to have the datasheet of 2n 2222 and there is nothing about the a331 code.

So yeah I did really try to figure it out before asking here :wink:

I do happen to have the datasheet of 2n 2222 and there is nothing about the a331 code.

Is it the right data sheet?
Click on the one in the link in reply #3 and look at the first page lower right.

I found it in your datasheet thanks.