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Questions and Answers
What are the three types of transistor connections?
The three types of transistor connections are common base, common collector, and common emitter.
In a common base connection, between which terminals is the input applied?
The input is applied between the emitter and base terminals.
What is the current amplification factor ($eta$) in a common-base connection?
The current amplification factor ($eta$, represented as $ rac{I_C}{I_E}$) is the ratio of output current to input current in the configuration.
How can the current amplification factor ($eta$) be increased in a common base connection?
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What is the significance of leakage current ($I_{cbo}$) in a common-base configuration?
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What factors influence the value of the current amplification factor ($eta$) in a common base connection?
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What happens to the collector current ($I_C$) in a common base connection?
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What is the typical value range for the current amplification factor ($eta$) in general-purpose transistors?
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Study Notes
Transistor Connections
- Transistors are three-terminal devices with an emitter, base, and collector lead.
- To connect a transistor in a circuit, two input and two output terminals are needed.
- One terminal serves as a common connection for both input and output.
- Three possible connections are: common base, common collector, and common emitter.
Common Base Connection
- Input is applied between the emitter and base.
- Output is taken from the collector and base.
- Base serves as the common terminal for both input and output circuits.
- Leakage current ($I_{cbo}$) flows in the collector circuit even when the emitter is open.
Current Amplification Factor ($\alpha$)
- Ratio of output current (collector current) to input current (emitter current) in a common base connection.
- Always less than unity.
- Increased by decreasing the base current, achieved through thinning and light doping of the base.
- Typical values range between 0.9 and 0.99 for general-purpose transistors.
- Affected by temperature, increasing with higher temperatures.
Collector Current Expression
- Not all emitter current reaches the collector.
- Some current is lost due to electron-hole combinations in the base region, contributing to base current.
- Leakage current also flows due to minority carriers in the reverse-biased collector-base junction.
- Total collector current ($I_C$) is the sum of the portion of emitter current reaching the collector and the leakage current.
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Description
Test your knowledge on transistor connections, specifically focusing on the common base configuration. Explore the principles of current amplification and the roles of the emitter, base, and collector leads. Understand the key characteristics that define their operation.
