2SD1257 Bipolar Transistor

• Type: NPN
• Collector-Emitter Voltage, max: 80 V
• Collector-Base Voltage, max: 130 V
• Emitter-Base Voltage, max: 7 V
• Collector Current − Continuous, max: 7 A
• Collector Dissipation: 40 W
• DC Current Gain (h_fe): 60 to 260
• Transition Frequency, min: 30 MHz
• Operating and Storage Junction Temperature Range: -55 to +150 °C
• Package: TO-252

Here is an image showing the pin diagram of this transistor.The 2SD1257 transistor can have a current gain of 60 to 260. The gain of the 2SD1257-P will be in the range from 130 to 260, for the 2SD1257-Q it will be in the range from 90 to 180, for the 2SD1257-R it will be in the range from 60 to 120.Sometimes the "2S" prefix is not marked on the package - the 2SD1257 might only be marked "D1257".You can replace the 2SD1257 with the 2SD1257A.