2N6121 Bipolar Transistor

• Type: NPN
• Collector-Emitter Voltage, max: 45 V
• Collector-Base Voltage, max: 45 V
• Emitter-Base Voltage, max: 5 V
• Collector Current − Continuous, max: 4 A
• Collector Dissipation: 40 W
• DC Current Gain (h_fe): 25 to 100
• Transition Frequency, min: 3 MHz
• 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 complementary PNP transistor to the 2N6121 is the 2N6124.You can replace the 2N6121 with the 2N5492, 2N5496, 2N6122, 2N6130, 2N6131, 2N6487, 2N6487G, 2N6488, 2N6488G, 2SC2075, 2SD1274, 2SD1274A, 2SD1274B, 2SD362, 2SD823, BD705, BD707, BD709, BD743, BD743A, BD743B, BD905, BD907, BD909, BDT91, BDT91F, BDT93, BDT93F, KSD362, MJE2801T, MJE3055T, MJE3055TG, MJF3055 or MJF3055G.