Which of the following is true for the cut-off region in an npn transi...
Both collector and emitter current are zero in cut-off region.
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Which of the following is true for the cut-off region in an npn transi...
Introduction:
The cut-off region is one of the operating regions of an npn transistor. In this region, the transistor is essentially turned off and no current flows through it. The potential difference between the emitter and the base plays a crucial role in determining whether the transistor is in the cut-off region or not.
Potential difference between the emitter and the base:
In the cut-off region, the potential difference between the emitter and the base is smaller than 0.4V. This is because the base-emitter junction is reverse-biased in this region, meaning the base is more positive than the emitter. This reverse bias prevents current flow across the junction, effectively turning off the transistor.
Explanation of options:
a) Potential difference between the emitter and the base is smaller than 0.5V: This statement is not true. The correct value for the potential difference in the cut-off region is smaller than 0.4V, not 0.5V.
b) Potential difference between the emitter and the base is smaller than 0.4V: This statement is true. As explained earlier, the potential difference between the emitter and the base must be smaller than 0.4V for the transistor to be in the cut-off region.
c) The collector current increases with the increase in the base current: This statement is not true for the cut-off region. In the cut-off region, the transistor is turned off, and no current flows through it. Therefore, the collector current is zero regardless of the base current.
d) The collector current is always zero and the base current is always nonzero: This statement is true for the cut-off region. In this region, the transistor is turned off, and no current flows through it. Therefore, the collector current is always zero, while the base current may still be nonzero.
Conclusion:
In summary, the correct statement for the cut-off region in an npn transistor is that the potential difference between the emitter and the base is smaller than 0.4V. This potential difference determines whether the transistor is turned off or not. Additionally, in the cut-off region, the collector current is always zero, while the base current may still be nonzero.
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