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Re: Uh-oh., Now I dood It. Q About Using Xistors for Diodes

In article , snipped-for-privacy@btopenworld.com mentioned...

Hiya! > > Get a dolls house, wire 50 of them in parallel across a mains cable. > Place them throughout the dolls house, and make your own hollywood > blockbuster exploding house effect!!

Sounds like a real blast! ;-)

However I'd use some real firecrackers for real FX.

I got a Q for all. These BC338s ae capable of handling an amp, as a transistor of course. WHat I need are some high conductance diodes that can handle high currents - less than an amp, maybe a half amp - and are reasonably fast switching. I was thinking of connecting the base and emitter together and using the collector junction as a diode. I fighre it should handle at least a couple hundred mA, maybe more. And since it's a fairly fast transistor, the diode should be so, too. Has anyone done somerthing like this? Anyone tried to measure the characteristics in a curve tracer?

I saw a schematic of an RF osc using 2 or 3 2N4401s connected as diodes as varicaps to modulate the oscillator. Thanks.

In seriousness tho, there are good buys to be had on E, as long as you > can use the things you buy - I've baught tubes of ICs years ago that are > still sitting here now, never got round to using them! > > Yours, Mark. > > Wats> > > I saw a bag of 1000 BC338 transistors on Ebay about ready for the > > bidding to end, and they were going for only $11.50, so I bid on them > > thinking that surely someone would outbid me. But they didn't! So > > now I'm the buyer of 1000 for only $12.50 plus $4 s&h, about a penny > > and a half each. Like I now have a lifetime supply of BC338s. Said > > they were new, and pic showed them in a labeled bag, but they might > > still be picked over and have low gain or whatever. > > > > I have to figure out how to use these up in my LED flashlights. > > They're about the same as a 2N4401, except capable of a bit more > > collector current. The BC337s I've been using work well, so I think > > I'll have a lotta uses for them. Oh, well..
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Reply to
Watson A.Name - "Watt Sun, Dar
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Bob Pease talks about using diode-connected transistors; e.g., as low-leakage diodes. But I think he means with base and collector connected, not base and emitter. If you poke around on the National web site for some of his online seminars I'm sure you can find info, including curves.

Half an amp times 0.7V is 0.35W. That's a fair amount of power for something that only has tiny little transistor leads; diodes get rid of their current through their big thick leads.

Reply to
Walter Harley

In article , snipped-for-privacy@cafewalterNOSPAM.com mentioned...

Thanks. The BC338 transistors are rated for an amp and 625 mW, so it should still handle that current. The transistor die is bonded to the collector lead, which is thicker than the other leads. If the collector lead is mounted close to the circuit board, most of the heat will be conducted away to the copper PCB traces. And now that I'll be getting a thousand of them, there's nothing saying I can't parallel a few. ;-)

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###Got a Question about ELECTRONICS?   Check HERE First:###
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My email address is whitelisted.  *All* email sent to it 
goes directly to the trash unless you add NOSPAM in the 
Subject: line with other stuff.  alondra101  hotmail.com
Don't be ripped off by the big book dealers.  Go to the URL
that will give you a choice and save you money(up to half).
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

Current hogging. And by the time you get a couple of low-value resistors to fix that, you might as well have just shelled out the dough for some bigger diodes.

(Hey! You callin' me a current hog? Well, you're a, a, a voltage weevil! Yeah!)

Reply to
Walter Harley

In article , snipped-for-privacy@cafewalterNOSPAM.com mentioned...

Heh-heh. Actually I figured that by coupling the DCTs closely thermally, the current hogging wouldn't be a problem. Just twist the leads together near the case. No resistors, no problem. I can also use some 1N5817 1A Schottky diodes; I got plenty of them. But I want to use the transistors since I have a bunch. So back to the original Q. How good a diode is a BC338 transistor with the E and B tied together and the collector used as the diode junction? Should I put a few on a PS and run various currents thru them and get some idea of the V drop at currents in the hundreds of mA? How would it be done in a commercial setting? Would they put a few on a curve tracer and run up the current to see how they performed? Thanks. Happy holidays.

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My email address is whitelisted.  *All* email sent to it 
goes directly to the trash unless you add NOSPAM in the 
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Don't be ripped off by the big book dealers.  Go to the URL
that will give you a choice and save you money(up to half).
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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

In article , Watson A.Name - "Watt Sun, Dark Remover" mentioned...

I went to the Central Semi website and checked out their reference manual. They have a .PDF index with the transistor types with each type a hot link that you can click on, which then downloads a .PDF of the actual die or chip that's used in that transistor.

formatting link
Click the page advance arrow until you go to 6 of 15. Then click on

2N3904 - CP192. You can see that the chip or die is only 13 x 17 mils. Then go to BC338 and you can see that the chip or die is 31 mil square, which is substantially larger area, and that's why it can handle a lot more current. 
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###Got a Question about ELECTRONICS?   Check HERE First:###
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My email address is whitelisted.  *All* email sent to it 
goes directly to the trash unless you add NOSPAM in the 
Subject: line with other stuff.  alondra101  hotmail.com
Don't be ripped off by the big book dealers.  Go to the URL
that will give you a choice and save you money(up to half).
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

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