In a common base amplifier circuit, calculate the change in...

In a common base amplifier circuit, calculate the change in base current if that in the emitter current is $2 \mathrm{~mA}$ and $\alpha=0.98$
(a) $0.04 \mathrm{~mA}$
(b) $1.96 \mathrm{~mA}$
(c) $0.98 \mathrm{~mA}$
(d) $2 \mathrm{~mA}$

Key Concepts

Calculating Base Current Change

To calculate the change in base current when there is a change in emitter current, the relationship I_B = I_E – I_C is employed. Given that I_C is a fraction (? times) of I_E, the change in base current can be determined by multiplying the change in emitter current by (1 – ?). This method is essential for analyzing how variations in the emitter current affect the base current in transistor circuits.

Transistor Current Relationships

In a transistor, the emitter current is the sum of the base current and the collector current. This fundamental relationship, derived from Kirchhoff's current law, is crucial for analyzing the behavior of BJTs. It allows for the determination of one current value if the other two are known and is applied in various amplifier configurations.

Common Base Amplifier

The common base amplifier is a configuration of bipolar junction transistors (BJTs) where the base terminal is common to both the input and output circuits. This configuration typically offers low input impedance and high output impedance, making it suitable for certain types of high-frequency applications. It is important in understanding how current and voltage are managed within transistor circuits.

Current Gain (?) in BJTs

?, the common base current gain, is defined as the ratio of the collector current to the emitter current (? = I_C / I_E) and is typically close to unity. This parameter indicates the efficiency with which the emitter current is converted into collector current and is essential when calculating the remaining base current, particularly in situations where changes in emitter current are involved.

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