regulator-waste-is-input-minus-output - Electronic Circuits XIII: Power, Rectification, and Regulation Step by Step

The input power budget closes as load plus waste. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

A linear regulator spends the voltage difference

The input minimum is 7 V while the output is 5 V. The difference is dissipated at the same load current.

P_{\text{waste}}=(V_{\text{in}}-V_{\text{out}})I

Input power closes as load plus waste in every row

The voltage difference stays fixed, so load power and waste power climb together with current.

\begin{array}{c|c|c|c}I&P_{\text{in}}&P_{\text{load}}&P_{\text{waste}}\\1\ \text{A}&7\ \text{W}&5\ \text{W}&2\ \text{W}\\2\ \text{A}&14\ \text{W}&10\ \text{W}&4\ \text{W}\\3\ \text{A}&21\ \text{W}&15\ \text{W}&6\ \text{W}\\\end{array}

Input power splits into load power plus waste

A linear training regulator spends the voltage difference at the same current.

7\ \text{V}\cdot2\ \text{A}=14\ \text{W}=10\ \text{W}+4\ \text{W}