2N6557 Bipolar Transistor

• Type: NPN
• Collector-Emitter Voltage, max: 250 V
• Collector-Base Voltage, max: 250 V
• Emitter-Base Voltage, max: 6 V
• Collector Current − Continuous, max: 0.5 A
• Collector Dissipation: 10 W
• DC Current Gain (h_fe): 40 to 180
• Transition Frequency, min: 200 MHz
• Operating and Storage Junction Temperature Range: -55 to +150 °C
• Package: TO-202

Here is an image showing the pin diagram of this transistor.The KST42 (SOT-23), MMBTA42 (SOT-23) and PZTA42 (SOT-223) is the SMD version of the 2N6557 transistor. These transistors are of the same type, have similar parameters and are designed for surface mounting.You can replace the 2N6557 with the 2N6558 or 2N6559.