Question

In a common emitter transistor amplifier, the output voltage and input voltage have a phase difference of

• A. $0^c$
• B. $\frac{\pi^c}{2}$
• C. $\frac{3\pi^\circ}{4}$
• D. $\pi^c$

Hint:

Common emitter amplifier gives phase reversal: \[ 180^\circ \text{ or } \pi \text{ rad} \]

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
A common emitter configuration causes a signal inversion due to the way the collector current affects the output voltage drop.
Step 2: Key Formula or Approach:
$V_{CE} = V_{CC} - I_C R_C$. An increase in input voltage increases $I_C$, which decreases $V_{CE}$.
Step 3: Detailed Explanation:
As input voltage rises, base current increases, collector current increases, and hence the voltage at the output (collector) drops. This opposite movement represents a $180^\circ$ or $\pi$ phase shift.
Step 4: Final Answer:
The phase difference is $\pi^c$.