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Questions and Answers
What happens to the depletion region as the voltage in forward bias increases?
What is the approximate cut-in voltage for a silicon diode?
Which statement best describes the current in reverse bias?
How does the resistance of a pn junction change in forward bias?
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What does a circuit symbol for a pn junction represent?
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Which term describes the behavior of a pn junction in relation to Ohm's law?
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Study Notes
- The behavior of a pn junction can be summarized in a graph of voltage versus current.
- In forward bias, when the positive terminal is connected to the p-type and the negative terminal is connected to the n-type, current flows from p to n.
- Initially, with a small voltage, the current is not significant due to the depletion region. As the voltage increases, the depletion region becomes smaller and the current grows. After a certain point, called the cut-in voltage, the depletion region vanishes and the current increases rapidly.
- The cut-in voltage for a silicon diode is approximately 0.7 volts.
- In reverse bias, when the positive terminal is connected to the n-type and the negative terminal is connected to the p-type, a very tiny current flows in the opposite direction from n to p. The current remains near zero and almost constant.
- The graph of reverse bias shows a constant near-zero current.
- The graph of forward bias shows a low current until the cut-in voltage, after which the current increases dramatically.
- A pn junction is a non-ohmic device, meaning Ohm's law does not apply to it.
- In forward bias, the pn junction has low resistance, while in reverse bias, it has high resistance to current.
- The circuit symbol for a pn junction represents the direction of conduction, with an arrow indicating conduction from p to n.
- A pn junction is also known as a pn diode, semiconductor diode, or junction diode.
- The word "diode" refers to a device with two terminals (p and n) that allows a path for charges to flow in one direction.
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Description
Explore the behavior and characteristics of a pn junction through a voltage versus current graph. Learn about forward bias, reverse bias, cut-in voltage, resistance, and more.