Application of Diodes

• The diode acts as a one-way valve for electric current. The anode is the negative side and points away from the battery, the cathode is the positive and points towards it.
• Diodes are similar to NPN transistors in that below 0.7V, very little current can pass through but once this is surpassed it allows it all through.
• Diodes can be used to prevent damage to polarised components in circuits.
• Protecting a npn transistor and MOSFET is very easy and requires the insertion of a silicon diode with the cathode connected to the positive rail (i.e. in reverse bias) of the circuit
• Diodes can be used to turn AC into DC by cutting out the negative voltage, by only allowing the current to flow in one direction. The process of changing AC into DC is called rectification.
• The voltage across the resistor, VR and the zener diode, VZ must add up to the input voltage.
• The zener diode must have a small current, the holding current, typically 5 to 10 mA flowing through it in order to maintain the zener voltage.