Question

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

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

Answer 1

Answer: (B)

Here,
Input signal, $v_1=2\cos \left(15t+\frac{\pi }{3}\right)$
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 $\pi \left(=180^{\circ }\right)$ between input and output signals.
$\therefore V_0=150\left[2\cos \left(15t+\frac{\pi }{3}+\pi \right)\right]$
$=300\cos \left(15t+\frac{4\pi }{3}\right)$