Fixed 5V rail, 1.5A continuous — the dropout trade-off
The L7805ACD2T-TR is a classic 5V fixed-output linear regulator from STMicroelectronics, delivering up to 1.5A continuous current from a maximum 35V input. The dropout voltage is 2V typical at 1A load, meaning the input must stay above 7V to maintain regulation at full current — a critical number for supply-rail headroom planning. The 68dB PSRR at 120Hz attenuates the ripple from a full-wave bridge, keeping output ripple low even with a poorly filtered bulk cap.
Dropout voltage and quiescent current — the thermal budget
At 1A output, the typical dropout is 2V, so a 7V input yields 2W dissipation in the pass element. The quiescent current is 6 mA, which is negligible for most loads but adds to the thermal load at high input voltage.
Active status, tape-and-reel supply, and package options
The base product number is L7805, and the D2PAK suffix indicates the surface-mount variant; through-hole TO-220 versions are also in the family if the PCB layout prefers leaded assembly.
Protection features and application fit
Built-in over-temperature shutdown and short-circuit protection cover the common failure modes — a sustained short or a thermal runaway condition will trigger the protection before the die cracks. No enable pin or power-good flag, so the output simply follows the input with a fixed 5V drop. Typical applications include post-regulator for a 9V or 12V rail, analog supply for op-amp circuits, or a clean 5V rail for microcontroller boards where the input is already regulated. The 35V max input allows it to survive transients on a 24V bus, but the dropout margin must be checked.