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ST offers the best of BJT and MOSFET in one single transistor

Posted: 21 Oct 2005 ?? ?Print Version ?Bookmark and Share

Keywords:stmicroelectronics? st? emitter-switched bipolar transistor? ebst? stc03de170?

STMicroelectronics (ST) introduced a family of hybrid Emitter-Switched Bipolar Transistors (EBST) designed for industrial three-phase auxiliary power supplies and Single-Ended Primary Inductance Converters (SEPIC) used as power factor pre-regulators in industrial lighting applications. According to the company, the new ESBT family resolves the power supply designer's dilemma of choosing either bipolar junction transistors (BJT), characterized by low conduction losses but slow switching speeds, or MOSFETs, with their fast switching speeds but high conduction losses.

Instead, explained ST, by incorporating a BJT and MOSFET connected in a cascode configuration and housed in a single package, the new devices retain the benefits of each approach while eliminating the disadvantages.

Another significant benefit of the new transistors is a high voltage capability of up to 1.7kV, which allows designs to operate with a higher flyback voltage and, consequently, a higher duty cycle. This, in turn, allows the power supply to handle higher powers or to operate within a wider range of input voltage.

Members of the new family include the STC03DE170, STC05DE150 and the STC08DE150, which feature breakdown voltages of 1.7-, 1.5- and 1.5kV, respectively, and on-resistances of 0.55-, 0.17- and 0.11 ohms. In comparison, 1,500V power MOSFETs typically exhibit on-resistances in the range 5 to 9 ohms.

All three new products feature a Vcs(sat) value of 0.9V, minimizing conduction losses, while the absence of tail currents also minimizes turn-off losses. As a result, ST said, the new ESBT family enables cooler and more reliable operation in all power supply applications from 30W to 150W. And by offering the industry's best combination of low forward voltage drop, high blocking voltage and fast switching speed, the ESBT series represents a breakthrough in the area of high voltage, high switching frequency applications, added the company.

All of the transistors are housed in a custom-designed four-lead TO-247 package, featuring a lateral collector pin to increase the clearance between high voltage and low voltage pins. The STC03DE150, STC03DE170 and STC08DE150 devices are available in production volumes, with pricing for sample (100 pieces) quantities of $3.10, $3.30 and $3.60, respectively.




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