Topic: Analog Circuits
Calculate the approximate power added efficiency of following power amplifier:
DC Voltage: 8 volts
DC Current: 5 Amp
AC Input signal: 0 dBm
O/P power: 30 dBm
- A. 25%
- B. 2.5%
- C. 40%
- D. 75%
Answer: B. 2.5%
Explanation: First, calculate DC Power: $P_{DC} = V \times I = 8 \text{ V} \times 5 \text{ A} = 40 \text{ W}$.
Next, convert input and output AC powers from dBm to Watts:
$P_{in} = 0 \text{ dBm} = 1 \text{ mW} = 0.001 \text{ W}$.
$P_{out} = 30 \text{ dBm} = 1 \text{ W}$.
Power Added Efficiency (PAE) = $\frac{P_{out} - P_{in}}{P_{DC}} \times 100\%$.
$\text{PAE} = \frac{1 - 0.001}{40} \times 100\% = \frac{0.999}{40} \times 100\% \approx 2.4975\%$, which is approximately $2.5\%$.