BC257B Bipolar Transistor

• Type: PNP
• Collector-Emitter Voltage, max: -45 V
• Collector-Base Voltage, max: -50 V
• Emitter-Base Voltage, max: -6 V
• Collector Current − Continuous, max: -0.1 A
• Collector Dissipation: 0.3 W
• DC Current Gain (h_fe): 200 to 450
• Transition Frequency, min: 180 MHz
• Noise Figure, max: 2 dB
• Operating and Storage Junction Temperature Range: -55 to +150 °C
• Package: TO-92

The BC257B is manufactured in a plastic TO-92 case. When looking at the flat side with the leads pointed downward, the three leads emerging from the transistor are, from left to right, the emitter, collector, and base leads.
Here is an image showing the pin diagram of this transistor.The BC257B transistor can have a current gain of 200 to 450. The gain of the BC257 will be in the range from 110 to 800, for the BC257A it will be in the range from 110 to 220, for the BC257C it will be in the range from 420 to 800.The complementary NPN transistor to the BC257B is the BC167B.The 2SA812 (SOT-23), BC857 (SOT-23), BC857B (SOT-23), BC857BW (SOT-323), BC857W (SOT-323), BC860 (SOT-23), BC860B (SOT-23), BC860BW (SOT-323), BC860W (SOT-323), BCW72 (SOT-23), BCW72LT1 (SOT-23), BCW72LT1G (SOT-23), KSA812 (SOT-23), KST5086 (SOT-23) and MMBT5086 (SOT-23) is the SMD version of the BC257B transistor. These transistors are of the same type, have similar parameters and are designed for surface mounting.You can replace the BC257B with the 2SA1127, 2SA1175, 2SA1246, 2SA1316, 2SA1317, 2SA1318, 2SA1391, 2SA1392, 2SA1481, 2SA1522, 2SA1523, 2SA1524, 2SA1525, 2SA1526, 2SA1527, 2SA1528, 2SA1529, 2SA608N, 2SA733, 2SA990, 2SA991, 2SB1116, 2SB1229, 2SB560, 2SB726, 2SB892, 2SB985, A733, H733, KSA733C, KSB1116, KSB1116S or NTE193A.