What values are needed to find the maximum available output wattage of a power supply?

• A. output voltage and output amperage
• B. input voltage and input amperage
• C. resistance and capacitance
• D. efficiency and temperature rating

Answer: (A)

The maximum output wattage comes from the output side of the power supply. You need the rated output voltage and the maximum output current. Multiply those two values to get the maximum watts the supply can deliver. Input voltage and input current describe what powers the supply from the wall, not what it can push out. Resistance and capacitance pertain to the load and circuit design, not the supply’s rated output capability. Efficiency and temperature rating affect how close you get to that maximum under real-world conditions and how heat limits performance, but they don’t set the base maximum on their own. For example, a supply rated at 12 volts and 5 amps can deliver up to 60 watts.