The OPA695 does not require an additional heat sink for most applications. The maximum desired junction temperature sets the maximum allowed internal power dissipation as described in this section. Do not exceed the maximum junction temperature of 150°C.

Operating junction temperature (T_J) is given by T_A + P_D × θ_JA. The total internal power dissipation (P_D) is the sum of quiescent power (P_DQ) and additional power dissipated in the output stage (P_DL) to deliver load power. Quiescent power is simply the specified no-load supply current times the total supply voltage across the device. P_DL depends on the required output signal and load. However, for a grounded resistive load, P_DL is at a maximum when the output is fixed at a voltage equal to one-half of either supply voltage (for equal bipolar supplies). Under this condition, P_DL = V_S 2 / (4 × R_L), where R_L includes feedback network loading.

Note that the power in the output stage and not into the load determines internal power dissipation.

As an absolute worst-case example, compute the maximum T_J using an OPA695IDBV (SOT23-6 package) in the circuit of Figure 6-1 operating at the maximum specified ambient temperature of +85°C and driving a grounded 100-Ω load.

This maximum operating junction temperature is much less than most system level targets. Most applications are lower as an absolute worst-case output stage power was assumed in this calculation.