Is Bipoler designed to withstand negative voltage and current?

They do not make major appliances last a long time because they know that your wife will say, "Honey, it looks old. Let's buy one that looks newer."

I took my daughter's fairly new white top of the line Microwave oven and refrigerator when she replaced them with stainless steel ones.

Aren't coffee makers, toaster ovens, and similar devices also considered appliances?

I tested 1/4 Watt resistors being pushed to 0.44 Watts and been shocked at how long they last. They burned off their enamel and then the resistance drifted upwards but at 22 Volts and 20mA, it took weeks before they suffered a catastrophic breakdown. I've pushed electrolytic capacitors way beyond their ripple current rating with the same result. OTOH, push that same capacitor 15° above its 105° rating and the life was measured in dozens of hours. The same held true for MOSFETS being pushed beyond their temperature or current ratings, but having the flyback out of an inductive load force it back into conducting was tolerated for weeks at a time.

I've yet to get stuck testing a BJT that was inadvertently being reverse biased but according to management, whether or not it works depends upon the number produced and the length of your warranty. A hobbyist can often push 100V diodes to 150V and get by with a single prototype. Build 100,000 power supplies with 3 year warranties and the verdict will be different.

My first colour TV was made in 1971. I fixed it every couple of years then I built a converter so it decoded Pay Per View for free.
It lasted 26 years until 1997 when its picture tube became dim. The replacement TV was a high quality Sony 32" colour TV that lasted only 8 years. My son found a much newer Sony 32" TV for $60 that I am still using today.

and appliances have to pass safety tests that prototypes don't..... and there's no warranty on a prototype. if it works, that's great, if it doesn't find out why and redesign it.

i always wonder how "transition" stuff makes it to market.... like "transition year" cars. or quite a few years ago a big push was on for "green" computer monitors (not green as in monochrome either). so what did a bunch of manufacturers do? they added a prototype shutdown circuit on a retrofit board, and rushed the "new" monitors to market. i'll give you 3 guesses (and the first two don't count) what the big failure item was in those monitors.... the "green" board of course....

I got stuck analyzing truss force diagrams for a four point linkage on Friday. The big question isn't whether an Electrical Testing Engineer can get something like that right but why an Electrical Testing Engineer is doing it in the first place. Wasn't a Mechanical Design Engineer expected to do that about 9 months ago?

We're all about "transition" products as in what kind of patch can we do to get this to do that and get it to market ASAP. Yep. There's always some design flaw or program bug that nobody in design engineering knew about or anticipated and nobody in management considers to be important, that is, not until customer service starts getting pummeled.

MrAl said:

Hi Jony,

Sorry i could not open your .asc file are you sure it is an asc file from LT spice or something else?

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Yes it's LT spice file.

It's quite a coincidence that you were able to measure the breakdown voltage of four transistors in different modes of operation and all four started to breakdown at exactly 5.5ma each.

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I force the current by using the current source.

Could it be that the breakdown voltages are really a little lower than that?

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Yes it's possible. But I also measure at 500uA

BC639
Vbe=7.7V; Vec=6.3V; I=500uA

BC337
Veb=7.9V; Vec=6,4V; I=500uA

2SC945
Veb=8.1V; Vec=7,5V; I=500uA

Also check this measurement
https://cr4.globalspec.com/thread/72501/Emitter-Base-Breakdown-Voltage-of-NPN-Used-as-Zener

Also, did you check the frequency response and gain of each transistor before and after the breakdown tests?

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No, I did not check that. But i read in the book that this emitter base breakdown voltage will cause degrade in some BJT parameters.

Hi Jony,

I tried to open that file in LT spice and it would not open. Are you sure you uploaded the right file? This happened once before and when the person went back and saved the file again and uploaded again it worked. I think this happened because the first time the person clicked "save" when the sim trace was in focus. The schematic itself has to be in focus when save is used.

Ok so you measured some of the transistors at 500ua. That's good too. What i was hoping to see was where the knee occurred. There could be some slope to the characteristic so it's a good idea to check the current where the junction starts to 'zener'. This would give results similar to this: (6.1v, 5.2ua) or maybe (6.2v, 43ua), so there would be two measured values not one set in advance and the other measured. Lowering the current slightly would result in a sort of much lower voltage, but raising the current slightly would result in a slight increase in voltage. The place where the knee occurs would be the measurement we are really after here.

Jony's file opens for me.

^ ...and me.

Hi,

Apparently it would not open from the browser 'open' command, but if i save it to a file first then it opens ok. Strange

It still cant find the .lib file however.

MrAl said:

Hi,

Apparently it would not open from the browser 'open' command, but if i save it to a file first then it opens ok. Strange

It still cant find the .lib file however.

Click to expand...

What .lib file?

Hi,

The transistor

MrAl said:

Hi,

The transistor

Click to expand...

The .asc file doesn't call a transistor lib file, does it?

Hi,


Ok i see what happened now. Originally the file would not open, then i found that if i saved the file first it would in fact open, but earlier someone else posted a file with a name very similar to this one called "base-emitter breakdown" which i had clicked on instead of "Vbe_Break1". That previous file required a .lib file for the transistor.

Now that i finally have the right file it seems to open ok
It's weird that it doesnt open using the browser open command though, but at least it works now.