BUL128B Bipolar Transistor

• Type: NPN
• Collector-Emitter Voltage, max: 400 V
• Collector-Base Voltage, max: 700 V
• Emitter-Base Voltage, max: 9 V
• Collector Current − Continuous, max: 4 A
• Collector Dissipation: 70 W
• DC Current Gain (h_fe): 25 to 40
• Operating and Storage Junction Temperature Range: -65 to +150 °C
• Package: TO-220

Here is an image showing the pin diagram of this transistor.The BUL128B transistor can have a current gain of 25 to 40. The gain of the BUL128 will be in the range from 14 to 40, for the BUL128A it will be in the range from 14 to 28.You can replace the BUL128B with the 2N6740, 2SC2335, 2SC2335-M, 2SC2898, 2SC3038, 2SC3038-M, 2SC3039, 2SC3039-M, 2SC3056, 2SC3056A, 2SC3057, 2SC3310, 2SC3447, 2SC3447-M, 2SC3750, 2SC3750-M, 2SC3795, 2SC3795A, 2SC4105, 2SC4105-M, 2SC4106, 2SC4106M, 2SC4107, 2SC4107-M, 2SC4108, 2SC4108-M, 2SC4160, 2SC4160-M, 2SC4161, 2SC4161-M, 2SC4162, 2SC4162-M, 2SC4163, 2SC4163-M, 2SC4164, 2SC4164-M, 2SC4242, 2SC5241, BUL128FP, FJP13007, FJP13009, KSC2335, KSC2335-R, KSC5021, KSC5021-O, KSC5021F, KSC5021F-O, KSE13005, KSE13007, KSE13007F, KSE13009, MJE13005, MJE13005G, MJE13007, MJE13007A, MJE13007G, MJE13009, MJE13009G, MJE13070, MJE13071, MJE16002, MJE16004, MJE8502, MJE8503, STD13007, STD13007-B, STD13007F, STD13007FC, STD13007FC-B, STD13007P or STD13007P-B.