The maximum power allowed to dissipate in a device is defined as:

where

• P_D is the power dissipation in a device
• T_J(max) is the maximum junction temperature
• T_A is the ambient temperature
• θ_JA is the thermal resistance of a particular package

For example, for the LM6171 in a SOIC-8 package, the maximum power dissipation at 25°C ambient temperature is 730 mW.

Thermal resistance, θ_JA, depends on parameters such as die size, package size, and package material. The smaller the die size and package, the higher θ_JA becomes. The 8-pin PDIP package has a lower thermal resistance (108°C/W) than the 8-pin SOIC-8 (172°C/W). Therefore, for higher dissipation capability, use an 8-pin PDIP package.

The total power dissipated in a device can be calculated as:

where

• P_Q = the quiescent power dissipated in a device with no load connected at the output.
  • P_Q = supply current × total supply voltage with no load
• P_L = the power dissipated in the device with a load connected at the output; P_L is not the power dissipated by the load.
  • P_L = output current × (voltage difference between supply voltage and output voltage of the same supply)

For example, the total power dissipated by the LM6171 with V_S = ±15 V, and the output voltage of 10 V into a 1‑kΩ load resistor (one end tied to ground) is: