How linear regulator dissipation works
The LM317 maintains about 1.25 V across R1. R2 sets the output and R3 represents the load. The input-to-output voltage drop times output current becomes regulator heat. Divider current contributes to that heat. This example requires at least 3 V of input headroom.
Nominal 1.25 V reference and 50 µA adjust current. Dissipation neglects small internal bias losses; it is not a junction-temperature or heatsink calculation. The mapped regulator model includes dropout and current limiting.
Change the form inputs or click a component value on the schematic. Choose Try in CircuitSim to simulate the configured circuit.