10.1.3 Power Dissipation

Power dissipation depends on power supply, signal, and load conditions. For DC signals, power dissipation is equal to the product of output current times the voltage across the conducting output transistor. Power dissipation can be minimized by using the lowest possible power-supply voltage necessary to assure the required output voltage swing.

For resistive loads, the maximum power dissipation occurs at a DC output voltage of one-half the power-supply voltage. Dissipation with AC signals is lower. Application Bulletin SBOA022 explains how to calculate or measure power dissipation with unusual signals and loads.

Figure 42. TO-220 Thermal Resistance vs Aluminum Plate Area

Figure 43. DDPAK Thermal Resistance vs Circuit Board Copper Area