A. Using the characteristics of Fig. 8 , determine the...

a. Using the characteristics of Fig. 8 , determine the resulting collector current if $I_{E}=3.5 \mathrm{~mA}$ and $V_{C B}=10 \mathrm{~V}$. b. Repeat part (a) for $I_{E}=3.5 \mathrm{~mA}$ and $V_{C B}=20 \mathrm{~V}$. c. How have the changes in $V_{C B}$ affected the resulting level of $I_{C}$ ? d. On an approximate basis, how are $I_{E}$ and $I_{C}$ related based on the results above?

a. Using the characteristics of Fig. 8 , determine the resulting collector current if $I_{E}=3.5 \mathrm{~mA}$ and $V_{C B}=10 \mathrm{~V}$.
b. Repeat part (a) for $I_{E}=3.5 \mathrm{~mA}$ and $V_{C B}=20 \mathrm{~V}$.
c. How have the changes in $V_{C B}$ affected the resulting level of $I_{C}$ ?
d. On an approximate basis, how are $I_{E}$ and $I_{C}$ related based on the results above?

Key Concepts

Transistor Output Characteristics

The output characteristics of a transistor are curves that represent the relationship between the collector current (IC) and the collector-base voltage (VCB) for various levels of the emitter current (IE). These curves illustrate how changes in the reverse bias across the collector-base junction can affect the collector current in the active region. Understanding these plots is key to analyzing the influence of voltages on transistor operation, particularly in relation to effects like the Early effect and biasing stability.

Early Effect

The Early effect refers to the phenomenon where the effective base width in a BJT decreases with an increase in the collector-base reverse bias voltage. This modulation of the base width affects the collector current, causing it to increase slightly with increasing collector voltage even when the emitter current remains constant. Recognizing and accounting for the Early effect is essential when predicting the performance of a transistor under varying voltage conditions.

Bipolar Junction Transistor (BJT) Operation

This concept covers the fundamental operation of a BJT, which is a three-layer semiconductor device consisting of emitter, base, and collector regions. Its operation is based on the control of the larger collector current by a smaller current injected into the base, making it an essential component in amplification and switching applications. Understanding the diverging current flows and the regions of operation (active, saturation, and cutoff) is crucial for analyzing transistor circuits.

Emitter and Collector Current Relationship

In BJTs, the emitter current (IE) is the sum of the base current (IB) and the collector current (IC), typically expressed as IE = IB + IC. In most practical situations, the base current is much smaller in magnitude compared to the emitter and collector currents; hence, IC is nearly equal to IE. This relationship simplifies circuit analysis and design, as it allows the approximation of the collector current directly from the emitter current under active region conditions.

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