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Which of the following correctly describes the most useful biasing conditions of the emitter-base and base-collector junctions (common base configuration) for a Bipolar Junction Transistor (BJT) among its different modes of operation?
Active Mode: Emitter-base junction is reverse-biased, and base-collector junction is forward-biased.
Active Mode: Emitter-base junction is forward-biased, and base-collector junction is reverse-biased.
Cut-off Mode: Both emitter-base and base-collector junctions are forward-biased.
Saturation Mode: Both emitter-base and base-collector junctions are reverse-biased.
Active Mode: Emitter-base junction is forward-biased, and base-collector junction is reverse-biased.
In the active mode of a BJT, the emitter-base junction is forward-biased to inject charge carriers into the base, while the base-collector junction is reverse-biased to sweep these carriers into the collector region. This biasing configuration allows the BJT to operate as an amplifier by controlling a large collector current with a small base current.
In the active mode of a BJT, the emitter-base junction is forward-biased to inject charge carriers into the base, while the base-collector junction is reverse-biased to sweep these carriers into the collector region. This biasing configuration allows the BJT to operate as an amplifier by controlling a large collector current with a small base current.
IEтАЛ=IBтАЛ+ICтАЛ тАФ Relationship between terminal currents
╬▒=IEтАЛICтАЛтАЛ тАФ Common base current gain
╬▓=IBтАЛICтАЛтАЛ тАФ Common emitter current gain
Forward-biasing the emitter-base junction lowers the potential barrier, allowing majority carriers to flow across the junction. Once in the base, these carriers (minority in the base) are then collected by the collector-base junction, which is reverse-biased to create a high electric field that effectively 'sweeps' them across, independent of the collector voltage (within limits).
Active Mode: E-B forward, B-C reverse (Used for Amplification).
Saturation Mode: E-B forward, B-C forward (Used for ON state in switching).
Cut-off Mode: E-B reverse, B-C reverse (Used for OFF state in switching).
Reverse Active: E-B reverse, B-C forward (Rarely used).
Linear amplification in active mode
High current gain
High switching speed in transistors
Thermal instability if not biased correctly
Input impedance variations with temperature
Signal amplification
Digital logic gates
Switching circuits
Option A is incorrect because E-B reverse and B-C forward defines 'Reverse Active' mode.
Option C is incorrect because cut-off mode requires both junctions to be reverse-biased.
Option D is incorrect because saturation mode requires both junctions to be forward-biased.
B is correct тАФ The active mode requires a forward-biased emitter-base junction and a reverse-biased base-collector junction for linear amplification.
Always remember the 'EB/CB' mnemonic: For Active Mode, think 'Forward then Reverse'. For Saturation, think 'Both Forward'. For Cut-off, think 'Both Reverse'.