Question

Identify the given transistor amplifier connection.

A. common base connection
B. common emitter connection
C. common collector connection
D. all of these

Answer 1

Hint-
The three electrical leads in a transistor are called the emitter, collector and the base. The following figure shows the positions of base, emitter and collector in the circuit symbol of a transistor.

Base is denoted as $B$, emitter is denoted as $$E$$ and collector is denoted as $C$.
Common Base configuration, is the configuration in which the base will be common between collector and emitter. That is, the base terminal will be common to the input signal and output signal.

Step by step solution:
A transistor is a three-terminal device. The three electrical leads in a transistor are called the emitter collector and the base. Analyze the following figure to identify the positions of base, emitter and collector in the circuit symbol of a transistor.

Base is denoted as $B$ emitter is denoted as $$E$$ and collector is denoted as $C$.
In common Base configuration, the base will be common between collector and emitter. The base terminal will then be common to the input signal and output signal that is why it is given the name common base.
In a common emitter configuration, the emitter will be common between collector and base. The emitter terminal will then be common to the input signal and outputs a signal that is why it is given the name common emitter.
In a common collector configuration, the collector will be common between emitter and base. The collector terminal will then be common to the input signal and output signal that is why it is given the name common collector.
From the circuit given in the question we can see that the base terminal is common to both collector and emitter. This means that the transistor is connected in common base configuration. The input current is current through the emitter, $I_E$ and the output current is through the collector, $I_C$.

Hence the correct answer is option A.

Note: Here, the arrow in the emitter terminal is directed outward which means it is an NPN transistor. If the arrow in the emitter terminal is directed inward then it will be a PNP transistor. Even if the transistor given in the circuit was a PNP transistor the configuration would be common base itself.