Equivalent Transistor.

*Correction: Ignore the statement about 0.5A max. I was looking at the datasheets for a 2N4401, and noticed that they themselves go up to 600 mA. No ceiling on this one.

Cannot get the image. Use any medium-signal NPN; that is to say, not small signal like the infamous 2N2222 whic would be a POS in that application. BTW, one does not drive a transistor base with voltage...

So you found a transistor...

No, the schematic I am basing my design from calls for a few

2N4401's. However, I am unable to aquire them, because the place I get components from does not carry any. The people who work there (think work-study undergrads), couldn't tell a diode from a toaster, so any querys as to what transistor would be a suitable replacement would go unanswered. I myself confuse electrical components with kitchen appliances from time to time as well, and I too don't know which transistors would work (hence this Usenet post directed at electronics experts/hobbyists). What I need is a list of parts numbers that you can say with complete certainty, "Yes, you can use this transitor instead of those for this application, and it will work as required". This way when I go to the stockroom with the elecrically illiterate, I can say "I need four 2Nxxx's. Do you carry those? No? How about 2Nyyyy's? 2Nzzzz's?". Get what I'm saying?

If you look at the schematic, you'll see that I needed about a dozen pieces. I have every part but the transistors, and the miniboard / soldering equipment should be coming in the mail tommorow. I'd like to get it all done by tommorow night, but If I don't know which trans. to get, I'll have to wait until monday or later to get em'. Not good news, seeing as this (moderately) simple project is about a week in the making, and has taken varying amounts of effort from a dozen people or so.

The 2N2222 will work in that application, they are cheap and abundant.

That's bull, even the PN2222A can handle 1A peak, and maintains a minimum HFE of 50 at 250mA with VCE,sat under 0.2V. It is a general purpose switching transistor, not small signal, and is competitive with the 2N4401 in most applications.

PN2222 is probably cheaper and easier to find. :-)

Then again, it's another number to hit the stockroom kids with. :-)

Cheers! Rich

BC337 is another substitute, besides 2N2222, that will work for you.

It's best to look at the datsheets for the transistors the supplier can provide you. No one here has a crossreference list to what's in stock at your supplier.

Ed

That's the best idea - find out what they've GOT, then look up the data sheets and find one that will work.

Just about any "general-purpose" NPN transistor should do.

Good Luck! Rich

Since the schamatic is inaccesable, i cannot help too much. NTE cross reference shows the 2N4401 as equivalent to their 123AP (TO-92 package, 600ma Ic max, 40Vce rating and 625mW max dissipation). Some other types that also cross to the 123AP are: 2N117, 2N118,

2N118A, 2N119, 2N120, 2N148C, 2N148C/D, 2N148D, 2N160, 2N160A, 2N161, 2N161A, 2N163, 2N263, 2N264, 2N385/46, 2N706/46, 2N706/51, 2N706A/46, 2N706A/51, 2N706B/46, 2N706B/51, 2N708/46, 2N709A/46, 2N......., 2N4400, 2N4401, 2N4420, 2N4421, 2N4422, 2N4432, 2N4432A, 2N4950, 2N4966, 2N4967, 2N4968, 2N......, 2N5769, 2N5810, 2N5845, 2N5845A, 2N5851, 2N.... und so wieder ad nauseum.

I see, from figure 3, page 4 that a pissy 2N2222 is shown. Look at the data sheet curves for the 2N2222 and you will see that they are decent to about 100mA and after that, internal losses become excessive. Hell, a TIP50 would be better in its sleep!

...and absolute shit above 100mA.

Excuse me! The original 2N2222 data sheet indicates "small signal" and the curves show that there are serious internal IR losses as one goes above 100mA; if one is crazy enough to attempt even 500mA, based on those specs, it would blow its cork! Now the PN2222A *might* be a little better due to a different die size and diffusion schedule. Looking at the Fairchild data sheet, please note there are no oerational specs or curves beyond 500mA, and those curves indicate that operation above 100mA can result in power dissipation tradeoffs that might not be acceptable. Furthemore operation at your vaunted one amp is certainly not recommended, as that is the *absolute maximum* rating!

That is about what i initially said..

That's not true, the transistor has been designed for maximal Hfe in that current range, and it is spec'd out to 500mA, which should give you a clue. You will be calling for a 2N3055 next.

Well, at least it wouldn't oscillate. ;-)

Cheers! Rich

I mannaged to acquire a few 2N2222's, and they work fine; however, after building the final version of the circuit, I uncovered a separate problem which is best discussed in a separate post (IC overheating).

Lemme see now; Philips has a max spec of 800mA in the *metal* can, and both Fairchild and Philips indicate a VCE(sat) of 1.6V (!!!) at

500mA - meaning an internal dissipation of 800mW nevermind the max dissipation spec is 500mW. I guess you love that loss and the smell of cooking silicon...