Switching Diode
Switching Diode (also called a Pulse Diode, Schottky Diode) – semiconductor diode used in pulse (discrete) systems. It mainly operates in switching configurations, which generate a pulse of only one sign (+), forward-bias. Depending on the application, switching diode can also operate as a simple rectifier diode,transient-voltage-suppressor or detection diode). It is characterized by a very fast operation rate (measured in nanoseconds, whereas for higher voltages – microseconds).
Most sought after parameters of switching diode, operating as a switching device are as follows:
- Very low resistance in the forward bias and very high resistance in the reverse bias,
- Switching process of the diode should occur as soon as possible (the least possible delay and no distortion of pulses).
Fig. 1. Switching Diode symbol
Switching Diode – Division
- Fast switching diodes – they are manufactured with application of semiconductor materials with a wider band gap (e.g. Gallium Arsenide (GaAs): trr < 0,1ns). Schottky diodes have significantly shorter switching times (small junction capacity Cj values) compared to regular semiconductor diodes (trr of 100ps), which is due to their junction construction”M-S” junction capacity,
- Low decay time diodes (also called step-recovery diode) – in this kind of diodes, storage of charge has a crucial impact on the diode operating speed. It is used to generate rectangular pulses (tf decay time must be very small).
Switching Diode – Limiting parameters
- IFmax – maximum constant bias,
- IFMmax – peak, maximum permissible diode bias,
- VRmax – maximum constant reverse voltage,
- VRMmax – maximum peak reverse voltage,
- Tj – permissible junction temperature.
Switching Diode – Static and dynamic parameters
- VF – forward voltage at a determined IF forward current (the higher the current, the greater the charge is stored on the pn junction diode basis and the defusing process is slower)
- IR – reverse current at a given VR reversing voltage (the higher the current, the faster the charge that is stored in the junction will be unloaded, diode will switch faster)
- Capacitance of the diode (at determined reverse voltage and frequency),
- trr– duration of diode switch (occasionally, instead of trr time, Qrr switching charge that is accumulated in connector is given).
Switching Diode – Characteristic
Characteristic of switching diode is shown below on Fig. 2.
Fig. 2. Illustration of the of diode switching process
Switching Diode – Applications
Short switching times of the Switching Diodes are sought after in many applications. Some of the most typical ones include:
- Voltage clamping,
- High speed rectifying and switching circuits,
- Reverse current and discharge protection,
- Switched-mode power supplies (as a rectifier).
Satya
I have a question??
How do you achieve the switching characteristics of diodes??
Plzz help me
admin
The reverse recovery time trr refers to the time it takes for the switching diode to turn completely OFF from an ON state. Generally, electrons cannot be stopped immediately after operation turns OFF, resulting in some current flow in the reverse direction.The higher this leakage current is, the greater the loss. However, reverse recovery time can be shortened through heavy metal diffusion, material optimization, or by developing FRDs (Fast Recovery Diodes) that suppress ringing after recovery.