2SD1221-O Bipolar Transistor

• Type: NPN
• Collector-Emitter Voltage, max: 60 V
• Collector-Base Voltage, max: 60 V
• Emitter-Base Voltage, max: 7 V
• Collector Current − Continuous, max: 3 A
• Collector Dissipation: 20 W
• DC Current Gain (h_fe): 60 to 120
• Transition Frequency, min: 3 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 2SD1221-O transistor can have a current gain of 60 to 120. The gain of the 2SD1221 will be in the range from 60 to 300, for the 2SD1221-GR it will be in the range from 150 to 300, for the 2SD1221-Y it will be in the range from 100 to 200.Sometimes the "2S" prefix is not marked on the package - the 2SD1221-O might only be marked "D1221-O".The complementary PNP transistor to the 2SD1221-O is the 2SB906-O.You can replace the 2SD1221-O with the 2SD1252, 2SD1252A, 2SD1253, 2SD1253A, 2SD1254, 2SD1254-R, 2SD1255, 2SD1255-R, 2SD1256, 2SD1256-R, 2SD1257, 2SD1257-R, 2SD1257A or 2SD1257A-R.