Popular transistors.

TIP31 transistor.

Type Designator: TIP31.
Package: TO-220, 1-base, 2-collector, 3-emitter.
Material of transistor: Si
Polarity: NPN
Total Devise power dissipation |PD|: 40W
Collector-base breakdown voltage |VCBO|:40V(TIP31),60V(TIP31A), 80V(TIP31B),100V(TIP31C)
Collector-emitter breakdown voltage |VCEO|:40V(TIP31), 60V(TIP31A), 80V(TIP31B),100V(TIP31C)
Emitter-base breakdown voltage |VEBO|: 5V
Maximum collector current |Ic max|: 3A
Maximum junction temperature |Tj|: +150 C
Transition frequency (ft) : 3MHz
Collector-emitter saturation voltage|VCE|: 1,2V(IC=3A,IB=375mA)
Forward current transfer ratio |hFE| : 50(IC=1 A,VCE=4V)