Question

In a transistor output characteristics commonly used in common emitter configuration, the base current ${I_B}$, the collector current ${I_C}$ and the collector-emitter voltage ${V_{CE}}$ have values of the following orders of magnitude in the active region
A) ${I_B}$ and ${I_C}$ both are in $\mu A$ and ${V_{CE}}$ in volts
B) ${I_B}$ is in $\mu A$ and ${I_C}$ is in $mA$ and ${V_{CE}}$ in volts
C) ${I_B}$ is in mA and ${I_C}$ is in $\mu A$ and ${V_{CE}}$ in mV
D) ${I_B}$ is in mA and ${I_C}$ is in mA and ${V_{CE}}$ in mV

Answer 1

Hint: To answer this question, it is important to understand the concept behind the configurations of the transistors. The transistor consists of three distinct regions namely, emitter, base and collector. So, there are three ways in which a transistor can be connected in a circuit, with one of the three being in common. The three configurations are:
i) Common Emitter configuration
ii) Common Base configuration
iii) Common Collector configuration

Complete step by step answer:
Consider the below transistor connected in a Common-emitter configuration:

As per the above figure, the configuration in which the emitter is connected between the collector and base is known as a common emitter configuration. The input circuit is connected between emitter and base, and the output circuit is taken from the collector and emitter. Thus, the emitter is common to both the input and the output circuit, and hence the name is the common emitter configuration.
Here, ${I_B}$ is the base-emitter current and ${I_C}$ is the collector-emitter current and the output voltage is given by –
${V_{CE}} = {V_{CC}} - {I_C}{R_C}$
Let us understand the working of the transistor in the CE configuration
In common emitter configuration, the input current ${I_B}$ is very small, so it is measured in micro ampere, $\mu A$.
The output voltage is given by, ${V_{CE}} = {V_{CC}} - {I_C}{R_C}$
 If the out voltage ${V_{CE}}$ applied to the collector base junction is further increased, the depletion region width further increases.
 The base region is lightly doped as compared to the collector region. So, the depletion region penetrates more into the base region and less into the collector region.
 As a result the width of the base region decreases in turn reducing the input current. And, it means that the output current or collector current, ${I_C}$is larger as compared to the base current ${I_B}$ and so, it is measured in milli-ampere (mA)
 As the output voltage increases from zero volt to different voltage level, since the cut in voltage is increased above 0.7 V so, in the active region the collector-emitter voltage or output voltage is measured in volts.
The output characteristics of CE configuration is the graph between output voltage ${V_{CE}}$ and collector current ${I_C}$. Here are the output characteristics for the CE configuration.

From the characteristics, it is clear that the output current stabilizes over sometime.
Hence from the above points we can say that:
The base current, ${I_B}$ is in $\mu A$
The collector current, ${I_C}$ is in $mA$
The output voltage, ${V_{CE}}$ is in volts, $V$

Hence, the correct option is Option B.

Note:
Since the emitter is connected to the ground, it is common to signals, input and output. The common-emitter circuit is the most widely used of junction transistor amplifiers, which can be used to increase the amplitude of the signals. This configuration can also be used as an electronic switch.