BC251 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: 0.35 W
• DC Current Gain (h_fe): 120 to 800
• Transition Frequency, min: 320 MHz
• Noise Figure, max: 2 dB
• Operating and Storage Junction Temperature Range: -55 to +150 °C
• Package: TO-92

The BC251 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 BC251 transistor can have a current gain of 120 to 800. The gain of the BC251A will be in the range from 120 to 220, for the BC251B it will be in the range from 180 to 460, for the BC251C it will be in the range from 380 to 800.The BC857 (SOT-23), BC857W (SOT-323), BC860 (SOT-23) and BC860W (SOT-323) is the SMD version of the BC251 transistor. These transistors are of the same type, have similar parameters and are designed for surface mounting.You can replace the BC251 with the BC307, BC556, BC557 or BC560.