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BUL741 Bipolar Transistor
Cost competitive Power Bipolar Transistor
for low power, current FED HF ballasts

BUL741 Product Page

The introduction of BUL741 will further enlarge ST’s wide product range for HF ballast applications, offering the best cost competitive product for low power solutions. The new BUL741 has been specifically designed to fit electronic ballasts of up to 2 x 32Watt in 120Volt push pull configuration and 277Volt half bridge in current FED topology.
  BUL741


Why Use BUL741?


Manufactured using multi-epitaxial planar technology with proprietary cellular emitter layout, the BUL741 is able to ensure the high current capability needed in half bridge current fed topologies and at the same time displaying outstanding dynamic performance especially in turn off. Additionally, an intermediate layer with increased thickness has been used to enhance the base collector junction breakdown capability (with the junction JBE reverse biased), allowing the bipolar to sustain high current levels in avalanche conditions.

BUL741 Features


High breakdown voltage, BVces = 1050V
Fast and tight switching times
Avalanche proof, Ear = 4mJ with L = 2mH
Available in popular TO-220, DPAK and IPAK packages

Excellent Performance


The multi-epitaxial planar technology, in addition to a specific base profile, helps to reduce the fall time and consequently the turn-off losses that are the most significant switching losses in standard operative conditions. An optimized control of the life time of the minority carriers brings tight dynamic parameters, leading to an increased total system efficiency in open load and short circuit operative conditions. The increased breakdown of the B-C junction means the bipolar device is able to sustain stressful tests like the “arching test”. The sudden change between open load and short circuit causes current spikes during the off-phase leading the BC junction into avalanche condition.

Range Extension


The BUL741 can be used in 2x32W lamp ballast circuits, with high cost/benefit ratio. The new BUL741 completes ST’s product range dedicated to the universal input half bridge in current fed topologies.

Power Bipolar For Universal Input Topologies


Part number
Icn
[A]
Power (up to)
[W]
Package
2.5
2 x 32
TO-220, DPAK, IPAK
3
3 x 32
DPAK
4
4 x 32
TO-220, DPAK, IPAK
5
140
TO-220, TO-220FP


BUL741 Schema
BUL741 in avalanche condition during the arching test.
The B-C junction acts as a zener diode, stopping the
rise of VCE above 1050V, avoiding device failure