1200 V / 8 A — the blocking voltage defines the application space
The STP08IE120F4 is an NPN Emitter Switched Bipolar transistor from STMicroelectronics' ESBT® series, rated for 1200 V collector-emitter blocking and 8 A continuous current. The 1200 V rating places it in the high-voltage switching class — the part is designed for circuits where the DC bus or rectified mains sits above 600 V, such as three-phase 400 VAC input stages or PFC boost converters running a 800 V rail.
Obsolete — last-time-buy window closed
STMicroelectronics lists the STP08IE120F4 as Obsolete.
TO-220-4 Full Pack — isolated tab, gate driver application
The TO-220-4 Full Pack (TO-220FP) package has a fully isolated plastic tab — no exposed metal pad, so the heatsink does not need an insulating washer. The fourth pin is the emitter-sense connection used in the Emitter Switched topology; this pin carries the gate-drive return current and must be routed directly to the driver ground, not shared with the power emitter path. The through-hole mounting suits point-to-point or PCB layouts where a single-sided board with a large copper island serves as the heatsink.
ESBT topology — what it changes for the gate drive
The Emitter Switched Bipolar (ESBT) is a cascode: a low-voltage MOSFET drives the emitter of a high-voltage NPN bipolar. The gate drive sees the MOSFET's threshold, not the bipolar's base charge — so the driver does not need to supply continuous base current. The turn-off is faster than a standard BJT because the MOSFET opens the emitter path, sweeping stored charge out of the bipolar. The trade-off is a slightly higher on-state voltage than a single IGBT at the same current density, but the switching losses at 20-50 kHz can be lower in a properly tuned resonant or quasi-resonant topology.