V-i characteristics - power semiconductor devices , Electrical Engineering

V-I Characteristics

 In the  normal  mode of  operation of an IGBT  a positive  voltage is applied to the collector relative to emitter. When  the gate is at zero potential with  respect to E no  collector current IC flows  for collector voltage VCE below the  breakdown level  VB. When VC < VB  and the gate voltage exceeds the threshold  value VGT, electrons  pass into the N- region ( base  of the P-N-p transistor).

1742_V-I Characteristics.PNG

                                                                        Figure V- I characteristics of IGBT

These electrons  lower the  potential of the N region  biasing the P+ - N_  junction thereby causing holes to be injected from  the P+  substrate into the N_ epi-layer region. The excess electrons and holes modulate the conductivity  N+ region which dramatically reduces the  on resistance of the device. With  zero gate  bins the forward characteristic  of  IGBT  shows  very low current (<1bA)  where it breaks up sharply to much larger current levels with only a slight  increase in voltage. The Vcharacteristics of IGBT  is shown  in figure  it show the relation  between  collector current  tc and collector to emitter voltage VCE  for different values of gate to  emitter  voltage VGE.

The junction J1 blocks reverse voltage. An IGBT  without  N+ buffer layer  has higher  reverse blocking  capability. Therefore  an IGBT  required  for blocking  high  reverse voltage  does not  have N+  buffer layer. The  reverse blocking voltage  is shown  as the VRM on the VI  characteristics. The junction J2 blocks the forward  voltage when the IGBT is off.

 

 

Posted Date: 4/2/2013 5:32:40 AM | Location : United States







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