The forward current goes into the longer lead (anode). This red LED (light emitting diode) does not have a stripe, but instead has wire leads of different length. The stripe (any contrasting color) corresponds to the diode’s cathode. The bar on the package is the bar of the diode symbol, so it indicates the cathode. There are a few ways to indicate which diode terminal is which.ĭiode packages like the glass and black plastic cylinders shown above usually have a painted bar near one end. Real-world diodes are so small there isn’t room to paint a little diode symbol on them, so you need to identify the terminals some other way.ĭiodes come in all sorts of tiny packages. If you are handling real diodes you have to figure out which way to point the diode. Identify the terminals of a real-world diode The big K kind of looks like a diode symbol.įlip the diode symbol around until it reads like a K. How can I remember the anode and cathode?įor the longest time I could not remember which end of the diode was the anode and which was the cathode – I looked it up every time. You will come across them in data sheets, the Anode and Cathode. You usually don’t need names for the two terminals. When you draw diodes, the symbol clearly indicates the direction of forward current flow. The diode’s voltage, $\goldD v$, is oriented with the $+$ sign on the end where forward current comes into the diode, just like the sign convention for passive components. The black arrow ► in the symbol points in the direction of the diode’s forward current, $\blueD i$. The schematic symbol for a diode looks like this, The details of how a semiconductor works are governed by quantum mechanics. Our ability to finely control the conducting properties of silicon allows us to create modern marvels like computers and mobile phones and every other complex electronic device. Other semiconductor materials include germanium (Ge, atomic number $32$, right below Silicon), and gallium-arsenide, a $1 : 1$ ratio of Gallium and Arsenic, also known as GaAs, (atomic numbers $31$ and $33$, on either side of germanium). B - boron, C - carbon, N - nitrogen, Al - aluminum, Si - silicon, P - phosphorus, Ga - gallium, Ge - germanium, As - arsenic. Part of the periodic table showing silicon (Si) and other nearby semiconductor materials. More is known about silicon than perhaps any other material on Earth. Silicon is by far the most common material used for creating semiconductor devices. The most well-known and well-understood semiconductor material is Silicon (Si, atomic number $14$) in the periodic table. Semiconductors usually act like insulators, but we can control how much they conduct by changing the way they are made – by adding faint amounts of impurity atoms – and by applying voltage. Semiconductor materials fall between insulators and conductors. Every diode you will come across in modern electronics is made with semiconductor material. Understand diode terms – forward bias, reverse bias, saturation current, and breakdown.Ī diode is any electrical device with the property that it conducts in one direction and not in the opposite direction. Learn to identify the terminals of a real-world diode – cathode and anode.
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