Class 12 Physics Semiconductor Electronics Common Emitter characteristics

Common Emitter characteristics

When the transistor is used in Common Emitter configuration, the input is measured between the base and the emitter; the output is measured between the collector and the emitter

Input characteristics

  • The variation of base current IBwith base-emitter voltage VBE is called input characteristics
  • While studying the dependence of IB on VBE , the collector-emitter voltage VCE is kept fixed
  • The current is small as long as VBE is less that the barrier voltage
  • When VBE is greater than the barrier voltage, the curves look similar to that of a forward biased diode
  • Input dynamic resistance of transistor –Input dynamic resistance of transistor (Ri) is defined as the ratio of change in base-emitter voltage δVBE to the resulting change in the base current δIB at constant collector-emitter voltage VCE

Ri = (  δVBE / δIB ) when VCE is constant

Output characteristics

  • The variation of collector current IC with collector-emitter voltage VCE is called output characteristics
  • While studying the dependence of IC on VCE , the base current IB is kept constant
  • From the graph, we see that as long as the collector-emitter junction is reverse biased, we get IC almost independent of VCE
  • We also find that for the given value of VCE, IC is large for large value of IB
  • Output dynamic resistance of transistor – Output dynamic resistance of transistor (Ro) is defined as the ratio of change in collector-emitter voltage δVCE to the resulting change in the collector current δICat constant base current IB

Ri = (  δVCE / δIC ) when IBis constant

Share these Notes with your friends  

< Prev Next >

You can check our 5-step learning process


.