PNP Darlington in an isolated TO-220FP tab
The STMicroelectronics TIP127FP is a PNP Darlington power transistor in the TO-220 Full Pack (TO-220FP) package, where the tab is fully isolated from the die. This saves an insulating washer and mica pad in through-hole mounting, though the thermal path to a heatsink runs through the plastic body rather than a metal tab.
The 100 V Vceo breakdown suits 48 V and 72 V DC bus rails common in industrial controls, motor drives, and solenoid drivers, with derating headroom for inductive flyback. The 5 A continuous collector rating is the DC limit; repetitive peak currents in a switching application should stay within the safe operating area. As a Darlington, the minimum DC current gain of 1000 at 3 A collector current and 3 V Vce means the base drive requirement is low — a microcontroller GPIO through a 1 kΩ resistor can typically saturate it. The trade-off is a saturation voltage of 4 V at 5 A, which drops about 20 W across the junction at full current — well above the 2 W package dissipation, so this part is used in switched loads with a low duty cycle or with a substantial heatsink on the TO-220FP face.
The standard TO-220 TIP127 (non-FP) is a common cross-shop candidate, but the Full Pack's isolated tab is a mechanical difference — the TO-220 version needs an insulator, which changes the assembly BOM and thermal resistance.