High-power diodes are used in automobiles, where they convert the AC from the alternator into DC that the battery and on-board electronics can use. Light emitting diodes LEDs , perfected in the early s, have replaced incandescent lamps for many purposes, and may soon replace the lamps used in car headlights and household light bulbs. Here is a partial list of the type of diodes invented, constructed and used over time, many comprise of hazardous materials:.
The S Tube Rectifier. The anode is a flat carbon electrode, and the cathode is cup-shaped, with a small tube-like opening, as illustrated. The tube contains helium at about 12 mm. When the anode is made positive, free electrons are drawn from all parts of the cup through the opening to the anode. In doing so they collide with the atoms of the helium and ionise them. The action is cumulative, and hence the tube conducts.
When the cup is made positive the action is very different. Positive ions in the cup, being much larger in bulk, are less mobile, and but comparatively few of them reach the cathode cup. The movement of the positive ions is so sluggish, and the number which reach the cathode so few, that the current conduction is less than 1 per cent. S tubes are manufactured for supplying D. They are rated at 20 watts each, the normal current being 50 milliamperes.
The tube has a practically constant drop of volts, and will stand 2, volts in the reverse direction. The concept of a diode mixer, no amplification ahead of it, remained for a long time. UHF tv tuners were, like that, maybe until the seventies.
In amateur radio circles converters for MHz and up generally lacked n RF stage and went right to a diode mixer. Until the late fifties there was no amplification, ten the parametric amplifier came along.
But it was transistors, that finally put rf amplification in such converters, slowly starting in the seventies. Silicon Si vs. The dead give-away: a forward voltage drop of higher than 0. Be careful out there. Perhaps another reader can, without guessing. But you knew that. Thanks for the tip on possible fakes diodes!
Enough is enough. One should consider the consequences of disallowed user autonomy. Any time I saw the number, I knew what it meant. But it was ten or fifteen years abo that I saw a photo of a real 1N34, it is a distinctive pckage. About the same time I went through a bunch of old boards looking for germanium diodes, and found quite a few, lingering on after silicon took over generally. If you look at germanium, schottky and silicon diodes with DMM set to the diode setting, and each type has a distinctive voltage shown.
So real Ge diodes are still out there, and still very very cheap. Ahh, Selenium rectifiers. Get them out of the parts box at least. Some people say burning garlic. Selenium is more dead skunk, rotten meat and a tire fire rolled into one with a side of cancer. That said there is some cool old electronics that use them, but as others said, a modern diode and adjusting the circuit to account for the lower drop will be more reliable, cooler, more efficient, more compact…. You could cobble together some squares if metal and paint the right color were they color coded?
I have some and they are different colors , then drill a home through the middle to put a silicon diode. So stripped them. And the selenium rectifiers are waiting fir the next toxic waste collection. Just be careful about doing that. A whole lot of negative Comments on here sadly, but I love these articles and they are well written! That is certainly a very interesting page! Leyden jar.. Argand lamp..
Gas lighting.. Incandescent light bulb.. Digital camera.. Miner's safety lamp.. Electric motor.. Variable resistor.. Powered hearing aid.. Magnetic recording.. Mercury-vapor lamp.. Electric vacuum cleaner.. Led light-emitting diode.. Color television..
Lava lamp.. It may be hard to believe, but the history of semiconductors dates back before that of the vacuum tube! The first primitive diodes, like the selenium rectifier or crystal detectors, used iron pyrites and galena as well as other natural copper oxides polycrystalline semiconductors. As refining techniques advanced, we entered the age where highly sensitive single crystalline semiconductors could be produced with reliability. The age of germanium and silicon.
During this time, we learned that germanium has a low resistance to heat, and so in today's world, most semiconductors are made with silicon. The diode element consists of a structure called the pn junction. The terminal attached to the p-type semiconductor is called the anode, and the terminal attached to the n-type semiconductor is called the cathode. Current is allowed to flow from the anode to the cathode, but almost completely prevented from flowing in the reverse direction.
This phenomenon is called rectification, and, put simply, it converts alternating current to a unidirectional current. Diode model Diode schematic electrical symbol.
As previously mentioned, if you were to think of an image that exemplifies the effects of a diode, you might think of it as a "valve" for electrical current.
If you think of electrical current as flowing water, the anode could be considered the upstream side and the cathode the downstream side. Water flows from upstream to downstream or shall I say, the electrical current does , but the "valve" prevents it from flowing from downstream to upstream. This is the principle operation of a diode. Today's diodes can be divided into two main classifications via junction: the pn junction and the Schottky barrier junction. The first one is a semiconductor-to-semiconductor junction, and this type of junction can be further classified into diffusion type junctions and mesa type junctions.
The latter one uses the effects caused between a semiconductor and a metal, and isn't actually a junction in terms of diodes. However, to make things easier to understand, it will be considered a junction here.
0コメント