Rectifier Diode - How it works
Diode as current valve
A diode is a semiconductor device that allows current to pass in only one direction. The ring marking indicates the cathode. This allows you to distinguish the connections from each other. The diode conducts when the anode is connected to the positive pin and the cathode to the negative pin.
Diode Characteristic Curve
The current-voltage characteristic describes the static behavior of a diode most clearly. The characteristic curve is divided into three sections: the forward bias, the reverse bias and the breakdown region:
Let´s explain some characteristic parameters and permissible limit values:
The Maximum Forward Current IFmax is as its name implies the maximum forward current allowed to flow through the device.
The Total Power Dissipation PDmax is the maximum possible power dissipation of the diode when it is forward biased (conducting).
Breakdown voltage VBR: At this voltage the diode changes gets damaged.
Peak inverse voltage PIV: It is the maximum reverse bias voltage that a diode can withstand without getting damaged. PIV is important in the design of rectifiers. You name it also Peak Reverse Voltage PRV.
Peak reverse voltage PRV: The same as Peak Inverse Voltage PIV.
The Maximum Operating Temperature is the maximum temperature allowable before the structure of the diode deteriorates and is expressed in units of degrees centigrade per Watt, °C/W. actually relates to the Junction Temperature TJ of the diode and is related to maximum power dissipation.
Application rectifier or signal diode:
- Rectification of alternating voltage
Free-wheeling diode as protection against dangerous voltage peaks when switching off inductances
Here, the free-wheeling diode is connected in parallel to the transistor, which acts as an electronic switch. The problem is: When an inductive load (motor, relay, etc.) is switched off, the created magnetic field contracts and generates a high negative voltage spike that can destroy the transistor. The freewheeling diode dissipates this negative voltage spike and thus protects the electronics.
- Decoupling of signals
- Reverse Polarity Protection