SBOS070D October 1997 – December 2019 OPA548
Plotting the load on the Safe-Operating-Area (SOA) curve allows the safety of the application to be assessed. Figure 40 depicts the 4-Ω load on the curve. With a resistive load, maximum dissipation occurs at an output voltage one-half of the supply voltage, in this case 7.5 V and 1.875 A for 22.5 W.
Consideration should be given to the condition of a shorted output. In this application this is a stress of 15 V at 2.5 A on the output stage, or 37.5 W which is just within the 50-W SOA of the OPA548. How long the circuit can withstand a short to ground will be determined by the size of the heatsink. Ultimately the thermal shutdown will activate providing short circuit protection, although even this is not recommended as a continuous condition.