Question 11.4: Amplifier Efficiency Find the input power, output power, sup...

The average signal power delivered to the amplifier is given by

P_i=\frac{V^2_i}{R_i}=10^{-11}\mathrm{~W}=10\mathrm{~pW}

(Recall that 1 pW = 1 picowatt = 10¹² W.) The output voltage is

V_o=A_{voc}V_i\frac{R_L}{R_L+R_o}=8\mathrm{~V~rms}

Then, we find the average output power as

P_o=\frac{V^2_o}{R_L}=8\mathrm{~W}

The supply power is given by

P_s=V_{AA}I_{A}+V_{BB}I_B=15+7.5=22.5\mathrm{~W}

and the efficiency of the amplifier is

\eta=\frac{P_o}{P_s}\times 100\mathrm{~percent}=35.6\mathrm{~percent}