Capacitors which leg is positive

The positive side is called the anode , and the negative one is called the cathode. The diode circuit symbol, with the anode and cathode marked. Current through a diode can only flow from the anode to the cathode, which would explain why it's important for a diode to be connected in the correct direction. Physically, every diode should have some sort of indication for either the anode or cathode pin.

Usually the diode will have a line near the cathode pin , which matches the vertical line in the diode circuit symbol. Below are a few examples of diodes. The top diode, a 1N rectifier, has a grey ring near the cathode. Below that, a 1N signal diode uses a black ring to mark the cathode. At the bottom are a couple surface mount diodes, each of which use a line to mark which pin is the cathode. Notice the lines on each device, denoting the Cathode side, which match the line in the symbol above.

LED stands for light-emitting diode , which means that much like their diode cousins, they're polarized. There are a handful of identifiers for finding the positive and negative pins on an LED. You can try to find the longer leg , which should indicate the positive, anode pin. Or, if someone's trimmed the legs, try finding the flat edge on the LED's outer casing.

The pin nearest the flat edge will be the negative, cathode pin. There might be other indicators as well. Sometimes it's easiest to just use a multimeter to test for polarity. Turn the multimeter to the diode setting usually indicated by a diode symbol , and touch each probe to one of the LED terminals.

If the LED lights up, the positive probe is touching the anode, and the negative probe is touching the cathode. If it doesn't light up, try swapping the probes around. The polarity of a tiny, yellow, surface-mount LED is tested with a multimeter. If the positive lead touches the anode and negative touches the cathode, the LED should light up. Integrated circuits ICs might have eight pins or eighty pins, and each pin on an IC has a unique function and position.

It's very important to keep polarity straight with ICs. There's a good chance they'll smoke, melt, and be ruined if connected incorrectly. DIP ICs usually have a notch to indicate which of the many pins is the first. If not a notch, the IC might have an etched dot in the casing near pin 1.

An IC with both a dot and a notch to indicate polarity. Sometimes you get both, sometimes you only get one or the other. For all IC packages, pin numbers increase sequentially as you move counter-clockwise away from pin 1. These ICs will usually have a dot near pin 1. Not all capacitors are polarized, but when they are, it's very important not to mix their polarity up. You can stick those in either way.

Through-hole and SMD 0. These are NOT polarized. Electrolytic caps they've got electrolytes , which look like little tin cans, are polarized. They might also have a longer positive leg. Applying a negative voltage for an extended period to an electrolytic capacitor results in a briefly exciting, but catastrophic, failure. Here are a few of the most commonly seen:. Need assistance with choosing the right capacitor for your operation?

Gateway Cable Company can help! Contact us for a quote on any of our products and to learn more about polarized and non-polarized capacitors. ISO Certified The plastic base of the capacitor are also chamfered on the positive or anode side. Footprint of a typical SMT can electrolytic capacitor. Capacitors of this type usually have tantalum or niobium inside but there are a few polymer electrolytic.

Case style means it is shaped similar to a resistor or ceramic capacitor. Unlike the other packages for capacitors , these are typically positive or anode marked. Watch out! Footprint for SMT case style electrolytic capacitors. Radial caps have both the anode and cathode leaving one side of the capacitor. PTH radial polarized electrolytic capacitor markings. Footprint for PTH radial style electrolytic capacitors. Axial style capacitors are not used very often but are interesting in how they are marked.

A negative or cathode band runs down the side of them similarly to the radial style but there is an arrow in the marking that indicates which side is negative or the cathode. PTH axial style electrolytic.