Question

When a triode is used as an amplifier the phase difference between the input signal voltage and output is

• A. zero
• B. $\pi$
• C. $\frac{\pi }{2}$
• D. $\frac{\pi }{3}$

Answer 1

Answer: (B)

$\pi$

Answer 2

Voltage gain of an amplifier $=\frac{\text { Output voltage }}{\text { Input voltage }}=-\frac{\mu R_{L}}{R_{L}+r_{P}}$ The negative sign indicates that the output voltage differs in phase from the input voltage by $180^{\circ}(\pi)$. This holds for a pure resistive load.