Question

The input signal given to a CE amplifier having a voltage gain of 150 is $v_i = 2 \cos \Bigg(15t+\frac{\pi}{3}\Bigg)$ The corresponding output signal will be

• A. $2 \cos \Bigg(15t+\frac{5\pi}{6}\Bigg)$
• B. $300 \cos \Bigg(15t+\frac{4\pi}{3}\Bigg)$
• C. $300 \cos \Bigg(15t+\frac{\pi}{3}\Bigg)$
• D. $75 \cos \Bigg(15t+\frac{2\pi}{3}\Bigg)$

Answer 1

Answer: (B)

$300 \cos \Bigg(15t+\frac{4\pi}{3}\Bigg)$

Answer 2

Here,
Input signal, $v_1=2 \cos \Bigg(15t+\frac{\pi}{3}\Bigg)$ and voltage gain, $A_v$ = 150
As $A_v=\frac{V_0}{V_i}$
$\therefore$ Output signal, $V_0=A_v V_i$
Since CE amplifier gives a phase difference of $\pi (=180^\circ)$ between input and output signals.
$\therefore V_0=150\Bigg[2 cos \Bigg(15t+\frac{\pi}{3}+\pi\Bigg)\Bigg]$
$=300 cos \Bigg(15t+\frac{4\pi}{3})$