2SD857A Bipolar Transistor

• Type: NPN
• Collector-Emitter Voltage, max: 80 V
• Collector-Base Voltage, max: 80 V
• Emitter-Base Voltage, max: 5 V
• Collector Current − Continuous, max: 4 A
• Collector Dissipation: 40 W
• DC Current Gain (h_fe): 40 to 250
• Operating and Storage Junction Temperature Range: -55 to +150 °C
• Package: TO-220

Here is an image showing the pin diagram of this transistor.The 2SD857A transistor can have a current gain of 40 to 250. The gain of the 2SD857A-P will be in the range from 120 to 250, for the 2SD857A-Q it will be in the range from 70 to 150, for the 2SD857A-R it will be in the range from 40 to 90.Sometimes the "2S" prefix is not marked on the package - the 2SD857A might only be marked "D857A".The complementary PNP transistor to the 2SD857A is the 2SB762A.The BDP951 (SOT-223) is the SMD version of the 2SD857A transistor. These transistors are of the same type, have similar parameters and are designed for surface mounting.You can replace the 2SD857A with the 2SC1986, 2SC2075, 2SC3851A, 2SD1267A, 2SD1274, 2SD1274A, 2SD1274B, 2SD613, 2SD772, 2SD792, 2SD823, BD243B, BD243C, BD537, BD539B, BD539C, BD539D, BD799, BD801, BD809, BD951, BD953, BD955, BDT83, BDT83F, BDT85, BDT85F, BDT87, BDT87F, BDX77, MJE15028, MJE15028G, MJE15030, MJE15030G, MJF15030, MJF15030G, TIP41D, TIP41E, TIP41F, TIP42D, TIP42E or TIP42F.