2SD666-B Bipolar Transistor

• Type: NPN
• Collector-Emitter Voltage, max: 80 V
• Collector-Base Voltage, max: 120 V
• Emitter-Base Voltage, max: 5 V
• Collector Current − Continuous, max: 0.05 A
• Collector Dissipation: 0.9 W
• DC Current Gain (h_fe): 60 to 120
• Transition Frequency, min: 140 MHz
• Operating and Storage Junction Temperature Range: -55 to +150 °C
• Package: TO-92MOD

Here is an image showing the pin diagram of this transistor.The 2SD666-B transistor can have a current gain of 60 to 120. The gain of the 2SD666 will be in the range from 60 to 320, for the 2SD666-C it will be in the range from 100 to 200, for the 2SD666-D it will be in the range from 160 to 320.Sometimes the "2S" prefix is not marked on the package - the 2SD666-B might only be marked "D666-B".The complementary PNP transistor to the 2SD666-B is the 2SB646-B.You can replace the 2SD666-B with the 2SC2274K, 2SC2274K-D, 2SC2383, 2SC2383R, 2SC3228, 2SC3228-R, 2SC3244, 2SD438, 2SD438-D, 2SD666A, 2SD666A-B, 2SD667, 2SD667A, 2SD667AB, 2SD667B, 2SD668, 2SD668-B, 2SD668A, 2SD668A-B, BC639, HSD1609S, HSD1609S-B, KSC1009C, KSC2310, KSC2383, KSC2383R, KTC3228 or KTC3228R.