BC557 Bipolar Transistor

• Type: PNP
• Collector-Emitter Voltage, max: -45 V
• Collector-Base Voltage, max: -50 V
• Emitter-Base Voltage, max: -5 V
• Collector Current − Continuous, max: -0.1 A
• Collector Dissipation: 0.5 W
• DC Current Gain (h_fe): 110 to 800
• Transition Frequency, min: 150 MHz
• Noise Figure, max: 2 dB
• Operating and Storage Junction Temperature Range: -65 to +150 °C
• Package: TO-92

The BC557 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 collector, base, and emitter leads.
Here is an image showing the pin diagram of this transistor.The BC557 transistor can have a current gain of 110 to 800. The gain of the BC557A will be in the range from 110 to 220, for the BC557B it will be in the range from 200 to 450, for the BC557C it will be in the range from 420 to 800.The complementary NPN transistor to the BC557 is the BC547.The BC857 (SOT-23), BC857W (SOT-323), BC860 (SOT-23) and BC860W (SOT-323) is the SMD version of the BC557 transistor. These transistors are of the same type, have similar parameters and are designed for surface mounting.You can replace the BC557 with the BC556 or BC560.