Output voltage vs output current

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SUMMARY

The discussion centers on the output characteristics of a transistor in common emitter (CE) mode, specifically the relationship between collector-emitter voltage (VCE) and collector current (IC). According to the equation VCE = VCC - IC RC, an increase in VCE results in a decrease in IC, which appears contradictory. The explanation lies in the behavior of charge carriers and the saturation of the transistor, where a small voltage remains across the collector-emitter junction even at saturation due to the presence of a series load resistor.

PREREQUISITES
  • Understanding of transistor operation in common emitter mode
  • Familiarity with the equation VCE = VCC - IC RC
  • Knowledge of charge carrier dynamics in semiconductor physics
  • Basic concepts of voltage drop across load resistors
NEXT STEPS
  • Study the characteristics of common emitter transistor configurations
  • Learn about transistor saturation and cutoff regions
  • Explore the impact of load resistors on transistor performance
  • Investigate charge carrier behavior in semiconductor devices
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Electronics engineers, students studying semiconductor physics, and anyone involved in designing or analyzing transistor circuits will benefit from this discussion.

ananthu
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In the output charecteristics of a transistor in CE mode, according to the eqation
VCE = VCC - IC RC it comes as when VCE increases IC
decreases and vice versa. But it is only because of the reverse collector-emitter voltage, the charge carriers are attracted to the collector side from the emitter side. Hence when the collector-emitter voltage increases collector current should also proportionally increase until it reaches the saturation value. Then why do we have a completely contradictory result in the above equation? According to this equation when collector-emitter voltage is maximum the collector current becomes zero and when the collector-emitter voltage is zero, the collector current becomes maximum! I need a logical explanation for it. My question is when the the collector-emitter voltage is zero how the collector current could become maximum as they can not reach the collector side at all as the acceleration given to them by the collector-emitter voltage will also be zero?
 
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The transistor does not have zero volts across it at saturation.
It always has a small voltage between collector and emitter.

I only has minimum voltage across it at that time because there is a series load resistor that drops most of the voltage reaching the transistor.
 
Last edited:

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