If a power amplifier has an output power of 10 W, and an amplifier gain of 16.4 dB, then the input drive power is:
A)400 mw
B)225 mw
C)229 mw
D)240 mw

Question

Quizplus · Accepted Answer

The gain in dB is given by $G_{dB} = 10 \log_{10} \left(\frac{P_{out}}{P_{in}}\right)$, where $P_{out}$ is the output power and $P_{in}$ is the input power. Rearranging for $P_{in}$, we get $P_{in} = P_{out} / 10^{(G_{dB}/10)}$. Substituting $P_{out} = 10W$ and $G_{dB} = 16.4$, we find $P_{in} = 10 / 10^{(16.4/10)} = 10 / 10^{1.64} = 10 / 43.65 \approx 0.229W$ or 229 mW.

If a Power Amplifier Has an Output Power of 10