BC257A 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): 110 to 220
• Transition Frequency, min: 180 MHz
• Noise Figure, max: 2 dB
• Operating and Storage Junction Temperature Range: -55 to +150 °C
• Package: TO-92

The BC257A 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 BC257A transistor can have a current gain of 110 to 220. The gain of the BC257 will be in the range from 110 to 800, for the BC257B it will be in the range from 200 to 450, for the BC257C it will be in the range from 420 to 800.The complementary NPN transistor to the BC257A is the BC167A.The 2SA812 (SOT-23), BC857 (SOT-23), BC857A (SOT-23), BC857AW (SOT-323), BC857W (SOT-323), BC860 (SOT-23), BC860A (SOT-23), BC860AW (SOT-323), BC860W (SOT-323), BCW71 (SOT-23), BCW71LT1 (SOT-23), BCW71LT1G (SOT-23) and KSA812 (SOT-23) is the SMD version of the BC257A transistor. These transistors are of the same type, have similar parameters and are designed for surface mounting.You can replace the BC257A with the 2SA1015, 2SA1020, 2SA1032, 2SA1048, 2SA1175, 2SA1246, 2SA1266, 2SA1267, 2SA1283, 2SA1315, 2SA1317, 2SA1318, 2SA1391, 2SA1392, 2SA1450, 2SA1481, 2SA1522, 2SA1523, 2SA1524, 2SA1525, 2SA1526, 2SA1527, 2SA1528, 2SA1529, 2SA1533, 2SA1534A, 2SA1619A, 2SA200, 2SA684, 2SA720, 2SA733, 2SA777, 2SA817, 2SA817A, 2SA935, 2SA953, 2SA954, 2SA984, 2SA984K, 2SA993, 2SB1229, 2SB560, 2SB647, 2SB740, 2SB764, 2SB892, 2SB985, A1015, A733, BC212, BC212A, BC636, H733, KSA1015, KSA539C, KSA708C, KSA733C, KSA931, KSP2907AC, KSP8598C, KSP8599C, KTA1266, KTA1267, KTA1274, KTA1281, KTA200, KTB764, PN3644 or PN3645.