BST39 Bipolar Transistor

• Type: NPN
• Collector-Emitter Voltage, max: 250 V
• Collector-Base Voltage, max: 300 V
• Emitter-Base Voltage, max: 5 V
• Collector Current − Continuous, max: 0.1 A
• Collector Dissipation: 1.3 W
• DC Current Gain (h_fe): 0 to 40
• Transition Frequency, min: 70 MHz
• Operating and Storage Junction Temperature Range: -65 to +150 °C
• Package: SOT-89

Here is an image showing the pin diagram of this transistor.The BST39 transistor is marked as "AT1".The complementary PNP transistor to the BST39 is the BST15.You can replace the BST39 with the BST40.