Aditya Mysore
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Does the collector current in a transistor depend on the base-collector voltage in a common base configuration? If so,how does it depend mathematically?
The discussion centers on whether the collector current in a common base bipolar junction transistor (BJT) depends on the base-collector voltage. Participants explore the mathematical relationships and physical principles governing this behavior, examining both theoretical and practical implications.
Participants generally agree that the collector current is influenced by the base-emitter voltage, but there is disagreement regarding the extent of the influence of the base-collector voltage, with some asserting it is negligible while others argue for its significance.
The discussion reflects varying interpretations of the relationships governing BJT operation, including the implications of the Shockley equation and the Early effect, without resolving the nuances of these concepts.
Thanks. Can you also explain physically why it does not depend on the voltage of the other junction?LvW said:The principle behaviour of a BJT does not depend on the specific configuration (common emitter, base or collector).
In any case, the famous Shockley equation applies: Ic=Is[exp(Vbe/VT) -1].
Hence, the collector current always is determined and controlled by the base-emitter voltage only.
I am aware that in some textbooks and other publications (in particular: Internet) it is stated that Ic would be controlled by Ib because of the relation Ic=B*Ib.
This relation holds, of course, and it is often used for designing simple transistor stages - however, it does not tell anything about cause and effect.
There are many properties and effects to be observed in BJT applications that can be explained ONLY with the above mentioned equation Ic=f(Vbe).
(I would not be surprised if this reply would cause some disagreements from other forum members; I have corresponding experiences.).
Aditya Mysore said:Thanks. Can you also explain physically why it does not depend on the voltage of the other junction?