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What is Semiconductor Diode?:

The Semiconductor Diode (Silicon Rectifier) described here in Fig 11.2(a) are based on the property of p-type and n-type materials in conjunction. An ideal diode presents zero impedance to current flow in one direction and infinite impedance in the opposite direction. A practical diode has a very low forward resistance and has a voltage drop of 0.3 to 0.7 V at all current levels and a reverse current of a few milliamperes when blocking voltage (or peak reverse voltage) is around 1 kV.

What is Semiconductor Diode

The v-i characteristic of a Semiconductor Diode and its idealized form, commonly employed in diode circuit analysis, are shown in Figs. 11.2(b) and (c) respectively. The voltage rating (maximum 5 kV), is fixed by the reverse characteristic in terms of the break-down voltage.

The main Parameters of Diode are:

  • Blocking voltage,
  • Average forward current and
  • Maximum operating junction temperature (nearly 125 °C for most silicon rectifiers).

Protection is necessary against voltage surges, overcurrents and excessive temperature rise. A “free-wheeling” diode is commonly used in motor control systems to provide an alternate path for continuity of current in the inductive circuit following the switching-off of some power device between the motor and the energy source.

The zener diode, though not a true power controlling device, is quite often used as a voltage control and sensing device in many motor controllers.