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Rohm 2N4403s - I'm Even More Convinced They're Cheap Knockoffs

I bought some 2N4403s with the R logo on them, all of them still on tape. Cost just a few dollars on Ebay. Well, I'm even more convinced they're cheap knockoff parts, or they've been culled. I pulled ten of them off the tape and tested them for beta at 10 mA, with both my ol' Heatkit IT121 transistor checker, and a cheap DMM. All of them had betas in the low 100s, mostly around 110 or 120, with one around 140. This is at 10 mA, at about a volt, as the test specifies in the data sheets. The Philips and On Semi data sheets guarantee 100 min at 10 mA, and 100 to 300 at 150 mA. Well, since the beta falls off as the current increases according to the chart in these data sheets, it seems to me that it's likely that the betas wouldn't make it to 100 at

150 mA. If so, they would be barely borderline.

All this, and the earlier discussion leads me to believe they're cheap knockoff parts, or seconds, culled from a large batch. Even so, they were put on tape for sale. Who knows?

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Reply to
Watson A.Name - "Watt Sun, Dar
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Any beta bin markings on them?

Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

Any markings or colored dots on the back?

Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

In article , snipped-for-privacy@interlogDOTyou.knowwhat mentioned...

Each transistor is marked:

R 2N

4403 E B C

Where the R is the logo. The tape they come on is unmarked.

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Reply to
Watson A.Name - "Watt Sun, Dar

According to the graph in my old Motorola transistor manual, the normalized DC gain (at 25C ) slope is very gradual, peaking at about 20ma and decreasing back to unity gain (normalized) at about 150ma. I read the chart as saying that if the gain at 1ma = 100, and at 10 ma it's140, then it will gradually decrease to 100 @ 150ma. If you are suspicious of your transistors, why not set up a test and measure the gain at 100ma? That would remove all doubt.

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In article , snipped-for-privacy@interlogDOTyou.knowwhat mentioned...

No markings or colorings. The "bellybutton" dimple cast into the back has some characters cast into it. Many have nothing, but some have two symbols such as: R3, I6, L4, O8, O5, L5, and some symbols look like they may be Japanese. Many of these have an overbar or an underbar on the first symbol. From what I've seen on the surface mount devices data sheets, this may be a date code.

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Reply to
Watson A.Name - "Watt Sun, Dar

I wouldn't be surprised. From the rare occasions I've had to go to RS, I've acquired a few bags of their resistor assortments. So far, every one that I've measured was right on the edge of the tolerance range.

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Reply to
Active8

: > All this, and the earlier discussion leads me to believe they're cheap : > knockoff parts, or seconds, culled from a large batch. Even so, they : > were put on tape for sale. Who knows? : >

: >

: I wouldn't be surprised. From the rare occasions I've had to go to : RS, I've acquired a few bags of their resistor assortments. So far, : every one that I've measured was right on the edge of the tolerance : range.

Thanks for bringing that up Mike. I thought there was something wrong with my DMM. Seems I found the same to be true, and mostly on the low side too.

Bill @ GarberStreet Enterprizez };-) Web Site -

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Reply to
Bill Garber

So you trust the meter again, I hope. I have no reason to suspect my meter, but I think I'd do well to get some calibration refs around here.

Your reader quotes ugly. What's your word wrap set at? I'm at 68.

HNY and good health in '04

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Active8

In article , snipped-for-privacy@att99.net mentioned...

With the DMM, I can't adjust the current; it's probably only a mA or less. But the Heathkit tester was made for up to a amp. But it suffered corrosion damage to the battery holder contacts when a battery leaked, so I did the earlier test with alli clips connecting the battery holder contacts to a pair of AA cells. At 100 mA, this wasn't giving stable readings, so I did the earlier tests at 10 mA.

So after reading this, I took the keystone battery holder out and replaced the contacts with a 4-40 screw, nut and nylon spacer from a transistor mounting kit. The old contact crumbled when I tried to clean off the corrosion, so it was the problem.

I took the ten 2N4403s and retested at 100 mA, and they did better at

100 mA than at 10 mA. Instead of only 110 to 120, they showed betas of around 140 at 100 mA. So apparently the Rohm 2N4403 doesn't conform to the graph that Philips shows in their data sheet, and the beta does increase at currents above 10 mA. Rohm's specs are the same as the Philips data sheet, so I thought it was safe to assume that the performance would be the same. I also checked the Fairchild data sheet and it also shows the graph without a 'hump' like the Philips graph.

Well, I gotta watch the Rose Parade so I'll followup later. ;-)

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http://www.everybookstore.com  You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
Reply to
Watson A.Name - "Watt Sun, Dar
[snip]

It is normal for transistors to have a beta "peak", an intermediary current at which beta is maximum. Above and below this value beta drops off.

You can amuse (and educate) yourself by simulating beta versus current varying model parameters ISE (base-emitter "leakage") and IKF (current crowding).

...Jim Thompson

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Jim Thompson

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