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Questions and Answers
In an NPN transistor, if the emitter-base junction is forward-biased, what constitutes the emitter current (Ä°E)?
In an NPN transistor, if the emitter-base junction is forward-biased, what constitutes the emitter current (Ä°E)?
- Equal parts electrons injected from the emitter into the base and holes from base to emitter
- Primarily electrons injected from the emitter into the base. (correct)
- Primarily holes injected from the base into the emitter.
- Only minority carriers from the base to the emitter.
For a PNP transistor, what primarily constitutes the emitter current (IE) when the emitter-base junction is forward-biased?
For a PNP transistor, what primarily constitutes the emitter current (IE) when the emitter-base junction is forward-biased?
- Primarily electrons injected from the emitter into the base.
- Primarily holes injected from the emitter into the base. (correct)
- Only minority carriers moving from base to the emitter.
- Equal parts electrons injected from the emitter into the base and holes from base to emitter.
Why is the conductivity of the emitter region made significantly higher than that of the base in a BJT?
Why is the conductivity of the emitter region made significantly higher than that of the base in a BJT?
- To ensure the current is primarily due to majority carriers from the emitter. (correct)
- To reduce the overall current flow through the transistor.
- To ensure that the current is mainly due to minority carriers.
- To achieve equal concentration of both majority and minority carriers.
In an NPN transistor, what happens to the electrons injected into the base from the emitter?
In an NPN transistor, what happens to the electrons injected into the base from the emitter?
If $I_E$, $I_C$, and $I_B$ represent the emitter, collector, and base currents respectively in a transistor, which equation accurately describes their relationship?
If $I_E$, $I_C$, and $I_B$ represent the emitter, collector, and base currents respectively in a transistor, which equation accurately describes their relationship?
What is the leakage current ($I_{CO}$) in a transistor?
What is the leakage current ($I_{CO}$) in a transistor?
What does the DC current gain ($\alpha_{dc}$) represent in a transistor?
What does the DC current gain ($\alpha_{dc}$) represent in a transistor?
Why is the value of $\alpha_{dc}$ typically less than 1?
Why is the value of $\alpha_{dc}$ typically less than 1?
What is the typical range of values for $\alpha_{dc}$?
What is the typical range of values for $\alpha_{dc}$?
What does the AC current gain ($\alpha_{ac}$) represent?
What does the AC current gain ($\alpha_{ac}$) represent?
How does the value of $\alpha_{ac}$ typically compare to that of $\alpha_{dc}$?
How does the value of $\alpha_{ac}$ typically compare to that of $\alpha_{dc}$?
According to the sign conventions for transistor currents, which direction is considered positive for current entering a terminal?
According to the sign conventions for transistor currents, which direction is considered positive for current entering a terminal?
Within the sign conventions for transistor voltages, when is a voltage considered positive?
Within the sign conventions for transistor voltages, when is a voltage considered positive?
If $V_{EB}$ is positive, what does this indicate?
If $V_{EB}$ is positive, what does this indicate?
A transistor is considered a how many terminal device?
A transistor is considered a how many terminal device?
What is a common practice when using a transistor as a two-port device?
What is a common practice when using a transistor as a two-port device?
What are the three terminals of a BJT?
What are the three terminals of a BJT?
In circuit diagrams employing NPN and PNP transistors, what dictates the direction of current flow?
In circuit diagrams employing NPN and PNP transistors, what dictates the direction of current flow?
Given a BJT circuit, how does one typically analyze it initially?
Given a BJT circuit, how does one typically analyze it initially?
Flashcards
IE= IC + IB
IE= IC + IB
The sum of collector current (Ic) and base current (IB) equals emitter current (IE).
Ico
Ico
Collector current resulting from minority carriers.
αdc (DC current gain)
αdc (DC current gain)
Ratio of collector current (Ic) to emitter current (IE) in DC conditions. Typically less than 1.
αac (AC current gain)
αac (AC current gain)
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Sign Conventions
Sign Conventions
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Three Terminal Device
Three Terminal Device
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Study Notes
- The Poisson distribution models the probability of a number of events occurring in a fixed interval, given a constant mean rate and independence from the last event.
Common Applications
- Modeling telephone calls to a call center per hour
- Modeling cars passing a point on a highway per minute
- Modeling customers entering a store per day
- Modeling defects in a manufactured product per unit
- Modeling meteorites greater than 1 meter diameter striking Earth per year
- Modeling goals scored in a soccer game
Probability Mass Function
- The probability of observing x events in a given interval: $P(X=x) = \frac{e^{-\lambda}\lambda^x}{x!}$
- Where x is the number of events
- $\lambda$ is the average number of events per interval
- e is Euler's number (approximately 2.71828)
Example Call center
- A call center receives 10 calls per hour on average.
- The probability of receiving exactly 5 calls in the next hour is calculated using the Poisson distribution:
- $P(X=5) = \frac{e^{-10}10^5}{5!} = 0.0378$
- There's a 3.78% chance of receiving exactly 5 calls.
Assumptions
The Poisson distribution relies on these assumptions:
- Events occur randomly and independently.
- The average rate of events $(\lambda)$ is constant.
- Probability of an event in a small interval is proportional to the interval's size.
- The probability of multiple events in a small interval is negligible.
Properties
- The mean of the Poisson distribution is $\lambda$
- The variance of the Poisson distribution is $\lambda$
- The standard deviation of the Poisson distribution is $\sqrt{\lambda}$
Example Factory
- A factory produces light bulbs with a 0.01 probability of being defective
- In a random sample of 100 light bulbs, we can use the Poisson distribution to approximate the probability of finding exactly 2 defective bulbs:
- $\lambda = np = 100 * 0.01 = 1$
- $P(X=2) = \frac{e^{-1}1^2}{2!} = 0.1839$
- There is approximately 18.39% chance of finding exactly 2 defective light bulbs in the sample
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