Step 1: Understanding the Concept:
Transistor amplifiers vary in their phase relationships. A phase shift indicates whether the output signal is inverted relative to the input.
Step 2: Detailed Explanation:
In a Common Emitter amplifier, the input is applied to the base and the output is taken from the collector.
When the input base voltage increases, the collector current increases.
This increased current causes a larger voltage drop across the collector resistor ($R_C$).
Since $V_{\text{out}} = V_{CC} - I_C R_C$, a larger drop results in a lower output voltage.
Thus, an increase in input results in a decrease in output, which is a $180^\circ$ inversion.
Step 3: Final Answer:
The phase shift in a CE configuration is $180^\circ$.