Diodes come in many shapes and sizes. High-current Diodes are often attached with a heat-sink device to reduce their operating temperature. It is possible to place Diodes in parallel to increase the current-carrying capacity, but the VI characteristics of both Diodes must be closely matched 2cl2FL to ensure that current divides smoothly (although a small resistor can be put in series with each diode to help equalize the currents). All Diodes have some seapage current (current that gets through when a diode is reverse-biased).
This seapage current-better known as the reverse current (IR)-is really small, typically within the nano ampere range. Diodes also have a maximum permitted reverse voltage, peak reverse voltage (PRV), or peak inverse voltage (PIV), above which a large current will flow in the wrong direction. If the PIV is maxed, the diode could get zapped and may become permanently damaged. The PIV for Diodes varies from a few volts to as much as several thousand volts. One method for achieving an effectively higher PIV is to place Diodes in series. Again, it is important that Diodes are matched to ensure that the reverse voltage divides equally (although a small resistor put in parallel with each diode can be used to equalize the reverse voltages).
Other things to consider about Diodes include maximum forward current (IF), capacitance (formed across the pn junction), and reverse recovery time. Most Diodes have a 1-prefix designation (e. grams., 1N4003). The two ends of a diode are usually famous from each other by a mark. For glass-encapsulated Diodes, the cathode is designated with a black band, whereas black-plastic exemplified Diodes use a white band. If no symbols exist (as seen with many power Diodes ), the cathode may be a bolt like piece. This piece is inserted via a heat-sink device (piece of metal with a hole) and is positioned down by a enthusiast. A fiber or mica machine is used to separate the cathode electrically from the metal heat sink, and a special silicon fat is defined between the machine and heat sink to enhance arctic conductivity.
A zener diode is a device that acts as a typical pn-junction diode when it comes to forward biasing, but it also has the capacity to conduct in the reverse-biased direction when a specific breakdown voltage (VB) is reached. Zener Diodes typically have breakdown voltages in the choice of a few volts to some hundred volts (although larger effective breakdown voltages can be reached by placing zener Diodes in series).