2SD1666 Bipolar Transistor

• Type: NPN
• Collector-Emitter Voltage, max: 60 V
• Collector-Base Voltage, max: 60 V
• Emitter-Base Voltage, max: 6 V
• Collector Current − Continuous, max: 3 A
• Collector Dissipation: 25 W
• DC Current Gain (h_fe): 70 to 280
• Transition Frequency, min: 40 MHz
• Operating and Storage Junction Temperature Range: -55 to +150 °C
• Package: TO-220F

Here is an image showing the pin diagram of this transistor.The 2SD1666 transistor can have a current gain of 70 to 280. The gain of the 2SD1666-Q will be in the range from 70 to 140, for the 2SD1666-R it will be in the range from 100 to 200, for the 2SD1666-S it will be in the range from 140 to 280.Sometimes the "2S" prefix is not marked on the package - the 2SD1666 might only be marked "D1666".The complementary PNP transistor to the 2SD1666 is the 2SB1133.You can replace the 2SD1666 with the 2SC1826, 2SC1985, 2SC1986, 2SC2075, 2SC3179, 2SC3252, 2SC3253, 2SC3254, 2SC3255, 2SC3746, 2SC3747, 2SC3748, 2SC3851, 2SC3851A, 2SD1134, 2SD1266, 2SD1266A, 2SD1274, 2SD1274A, 2SD1274B, 2SD1354, 2SD1406, 2SD1761, 2SD1913, 2SD313, 2SD613, 2SD823, 2SD880, BD203, BD241A, BD241B, BD241C, BD243A, BD243B, BD243C, BD303, BD535, BD537, BD539A, BD539B, BD539C, BD539D, BD543A, BD543B, BD543C, BD545A, BD545B, BD545C, BD797, BD799, BD801, BD807, BD809, BD949, BD951, BD953, BD955, BDT81, BDT81F, BDT83, BDT83F, BDT85, BDT85F, BDT87, BDT87F, BDX77, D44H11, D44H11FP, D44H8, KSD1406, KSD2058, KSD880, KTD1351, MJE15028, MJE15028G, TIP41D or TIP42D.