Did I make a bad purchase with these 2n2222A's?

[Gus]

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You should be able to build a good Si FF with what you bought.
Beta changes with how the test is done different testers will give different readings 2nd link has a table in reply 1 that are real measurements I took.
I like 2N2222s around 200

Others have posted circuits there are calculators and LT spice etc. to help adjust FF like circuits

Two threads I started that might help

https://www.diystompboxes.com/smfforum/index.php?topic=114153.msg1059002#msg1059002

https://www.diystompboxes.com/smfforum/index.php?topic=114210.msg1059667#msg1059667

[GuitarMatt]

Thanks mozz, my "reputable seller" designation was based purely off his good eBay seller rating.

Is it really that common for electronic parts like this to be fake? I can understand why somebody would sell bogus parts, but couldn't they just as easily do it by trying to pass it off as NOS, or putting it in a metal casing before relabeling it? I thought that was part of why we test their gains, so regardless of their external casing, you know something about how it behaves.

How would I verify the authenticity of "old date codes"? I'm totally new to this sort of thing.

Thank you Gus, I will definitely check out those threads!

[jfrabat]

I have used (and have stock of) 2N2222 in TO-18 and TO 92.  They work nicely for pedals.  Don't throw them away...  try them and see if you like them.  That's the beauty of breadboarding!

[PRR]

> If i see a TO 92 package, it is most likely some other transistor that way exceeds the 2n2222a spec, and is relabeled.

"PN2222" (plastic 2222) was a thing, probably legitimately out-sold TO-18 metal 2222, and was a 2222 die inside.

Seeing the plastic part marked "2N2222" defies the JEDEC registration papers. Like you can't get an AKC registration for a Corgi with a tail. You wonder what else they are not telling you.

(Yes, I know you can get AKC papers for a rock, as long as you never enter it in a show or have an unhappy breeding.)

[GuitarMatt]

PRR, I don't follow. Are you saying PN2222's are likely different from the 2N2222's I have?

Also can anyone tell me what the A means at the very end of (2N2222A)? What does a B at the end mean? I thought it had something to do with the gain, but I really don't know.

[Rob Strand]

Now my understanding is that the hfe should be around 100, but I got them today, and tested them with both a built-in multimeter tester and the GeoFX transistor tester, and they all have gains around 250 with little variation. None are below 200.

They are not off spec.  It's a matter of how to interpret the datasheet. In the end the tabulated data was for a different part, 2N2222, not 2N2222A.

The tabulated data on a datasheet can show a combination of minimum, typical and maximum values.
You will see that hFE can vary quite bit with collector current.

Sometimes you will see different specs and different presentation of specs in the datasheets for different brands.


Using your table,
https://postlmg.cc/sBnNHGkf

From the 150mA current, min=100 and max=300.     So max is 3 times min (roughly).  At a more reasonable 1mA your table has hFE min =50, so you might guess hFE max = 150 and on average hFE typ. about 100.

However, look at the figure 1 on this datasheet, showing typical value
https://web.mit.edu/6.101/www/reference/2N2222A.pdf

Here the gain is about 225.   In fact in this datasheet the tabulated data for 1mA shows hFE min = 75 and hFE max = 325, so you could guess a typical of about 200.   Either way you getting values of around 200.

So the short answer the 200 you measured sounds fine.

One issue is there is 2N2222A's and 2N2222's maybe your table is for a 2N2222, which IIRC has lower gain.

EDIT:
OK it's confirmed the table is for 2N2222 not 2N2222A

https://media.digikey.com/pdf/Data%20Sheets/ST%20Microelectronics%20PDFS/2N2222.pdf

[Gus]

Used PN2222s in the linked thread. I like this adjustment of the FF. Notice the collector voltages Q2 does not have to be 1/2 power supply voltage.
https://www.diystompboxes.com/smfforum/index.php?topic=112880.msg1044061#msg1044061

[anotherjim]

And to anotherjim, I can try to reverse beta, but I have never heard of that before. If I do that on a transistor with gain of 250, what could I reasonably expect the new gain to be? Edit: I just reversed some with gains of about 280 and they came back at 20 or lower. Interesting, but probably too low to be usable.

I'm not a FF expert -  but doesn't the circuit effectively multiply the gains of the transistors? 100x100 is same as 20x500 - in principle. Bear in mind that the average Hfe of germaniums is around 70. There's some fuzz designs out there with intentional reverse beta which used to catch me out as I assumed an error in the schematic.

Anyway, you can socket mount transistors -  use or butcher an IC socket if you have to - and get building!

[zombiwoof]

PRR, I don't follow. Are you saying PN2222's are likely different from the 2N2222's I have?

Also can anyone tell me what the A means at the very end of (2N2222A)? What does a B at the end mean? I thought it had something to do with the gain, but I really don't know.

The "A" suffix means they are sorted for gain ranges, A is lowest, B is medium gain, and C would be the highest gain range for that particular transistor.  If no suffix, they are unsorted for gain, and can be anywhere within the full range for that transistor.
That is my understanding.
Al

[duck_arse]

in the 2N/PN types, the A suffix indicates an improved process over the first, non-A spec parts. usually an obscure current or voltage spec. as far as I know, 2N/PN issue a different type number for gain-ranging.

and - the silicon die inside the xx2222A should be the same whether 2N or PN, BUT the 2N should be a metal can, and the PN should be a plastic. those transistors shown at eebay, with 2N2222 etched on, and no other markings are suspect. will almost certainly work as transnsitors, but you have no real idea what the die inside is.

the Pro Electron series transistors, ACxxx, BCxxx et al use the A, B, C suffixes for gain bukketing.

[Marcos - Munky]

Assuming I'll need to make another purchase, does anyone have any suggestions on silicon transistors that are generally useful for fuzz-face type builds with gains that are within 70 to 130?

PN2369A have hfe between 40 and 120.

[Gus]

Can't get the attachment to work otherwise there would be a screenshot of the circuit

Simmed the stock Si FF circuit you find on the web with LT spice using the 2N2222 models.

Change the Q1 33K to 10k and the 1K gain control to a 2K or the 1K with a fixed 1K from the bottom to ground. The cap on the control bypasses the fixed 1K all the time
The rest is the 470 and 8.2K in the collector, 100k feedback bias. Cap values and output volume control value to taste

The LT spice 2N2222 model seems to give good results in simple gain stages like a FF, often the circuit voltages match the sim with the 2N2222 model
Simmed at Q1 collector 1.6VDC and and Q2 collector 4.6VDC with the two resistor value changes.

With Fuzzes like this don't get stuck at the 1/2 supply voltage at Q2 like you might read on the web.

[PRR]

> The "A" suffix means they are sorted for gain ranges

That's true of many later EU and Japan parts.

It is not generally true in 2N registration. And the 2N2222A is a modestly improved (higher Vceo) 2N2222.

Selecting for hFE is doomed to be a long hunt.

[Rob Strand]

in the 2N/PN types, the A suffix indicates an improved process over the first, non-A spec parts. usually an obscure current or voltage spec. as far as I know, 2N/PN issue a different type number for gain-ranging.

It is not generally true in 2N registration. And the 2N2222A is a modestly improved (higher Vceo) 2N2222.

Yes, for 2N part's it means a new revision, or in fact a new part which is "better" than it's older brothers.

2N/PN issue

In the back of my mind I thought PN meant plastic and cheaper.   There was also MPS/MPSA parts.    IIRC pin-outs came into the picture as well.

The metal can BC108s became plastic BC548's more or less.   There was an era when the plastic parts replaced metal cans.
------------------------------------
EDIT:

Here's an example of the MPS2222/MPS2222A
https://www.farnell.com/datasheets/115091.pdf

For these one's at least the pin-out looks normal for 2Nxxxx
-----------------------------------
For good measure here's the PN2222.    The weird thing is this 2018 datasheet from ON Semi doesn't have the PN2222A in the title, and has a lot of stuff stripped out,
https://www.onsemi.com/pub/Collateral/PN2222-D.PDF


This older 2000 datasheet is a combined datasheet and implies the PN2222 is superceded by the PN2222A,
https://users.ece.utexas.edu/~valvano/Datasheets/PN2222-D.pdf

It seems the datasheets are suffering from cut-backs these days 

[PRR]

> I thought PN meant plastic and cheaper.

Plastic, lower cost. Not a lower quality!

Military and gear-heads clung to metal packages even after improved epoxy was shown to be better in almost all ways.

[dennism]

Since you've got it on breadboard anyhow, try putting a very small value cap (try 47 or 51 pf) across the collector and base of each of the  transistors.    It's a great way of smoothing out a silicon fuzz face and generally allows you to get away with higher hfe transistors than you might otherwise.

[Gus]

Found the thread with a one knob fuzz with 2N2222 transistors. I have built a few of this circuit. Parts to the left are a simple guitar sim.
Think colorsound or meathead like fuzz
I used PN2222 transistors and metal mot 2N2222 transistors no real difference it is fuzz it about distortion
https://www.diystompboxes.com/smfforum/index.php?topic=112880.msg1044061#msg1044061

[Rob Strand]

Totally unrelated to the original problem, but I tried to pin down when the plastic packages appeared.

BC108 (TO-18 metal can) and BC548 (TO-92 plastic)

BC548's were released around 1973


History from ETI Electronics magazine in AU:
Ad's appears for BC548's around late 1973
1974 project parts lists specify only BC108
1975 project parts lists specify both BC108 and BC548 as equivalents
1976 projects parts list specifiy only BC548's, BC108's no longer appear
          BC108's were being sold off in bulk in 1976 ads.

There's a few exception but that's the general trend.