The OPAx863 does not require heat sinking or airflow in most applications. The maximum allowed junction temperature sets the maximum allowed internal power dissipation. Do not allow the maximum junction temperature to exceed 150°C.

Operating junction temperature (T_J) is given by,

where

• T_A is the ambient temperature
• P_D is the total power dissipation internal to the amplifier
• R_ƟJA is the junction-to-ambient thermal resistance

The total power dissipation P_D = P_DQ + P_DL

where

• P_DQ = (V_S+ ‐ V_S-) x I_Q, is the power dissipation due to the amplifier quiescent current
• P_DL(max) = V_S² / (4 × R_L), is the internal power dissipation due to the output load current

As a worst-case example, compute the maximum T_J using an OPA2863-DGK (VSSOP package) configured as a unity gain buffer, operating on ±6-V supplies at an ambient temperature of 25°C and driving a grounded 500-Ω load.

Maximum T_J = 25°C + (0.042 W × 180.3°C/W) = 33°C, which is much less than the maximum allowed junction temperature of 150°C.