Popular transistors.

TIP31 transistor.

Marking: TIP31.
Package: TO-220, 1-base, 2-collector, 3-emitter.
Material of transistor: Si
Polarity: NPN
Total Devise power dissipation |P_D|: 40W
Collector-base breakdown voltage |V_CBO|:40V(TIP31),60V(TIP31A), 80V(TIP31B),100V(TIP31C)
Collector-emitter breakdown voltage |V_CEO|:40V(TIP31), 60V(TIP31A), 80V(TIP31B),100V(TIP31C)
Emitter-base breakdown voltage |V_EBO|: 5V
Maximum collector current |I_{c max}|: 3A
Maximum junction temperature |T_j|: +150 °C
Transition frequency (f_t) : 3MHz
Collector-emitter saturation voltage|V_CE|: 1,2V(IC=3A,I_B=375mA)
Forward current transfer ratio |h_FE| : 50(I_C=1 A,V_CE=4V)