BF421 Bipolar Transistor

• Type: PNP
• Collector-Emitter Voltage, max: -300 V
• Collector-Base Voltage, max: -300 V
• Emitter-Base Voltage, max: -5 V
• Collector Current − Continuous, max: -0.05 A
• Collector Dissipation: 0.8 W
• DC Current Gain (h_fe): 50
• Transition Frequency, min: 60 MHz
• Operating and Storage Junction Temperature Range: -55 to +150 °C
• Package: TO-92

The BF421 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 complementary NPN transistor to the BF421 is the BF420.The BF621 (SOT-89) and BF821 (SOT-23) is the SMD version of the BF421 transistor. These transistors are of the same type, have similar parameters and are designed for surface mounting.You can replace the BF421 with the 2SA1091-O, 2SA1371-D, 2SA1371-E, 2SA1371-F, 2SA1624, 2SA1624-D, 2SA1624-E, 2SA1624-F, 2SA1625-K, 2SA1625-L, 2SA1767, 2SA1767Q, 2SA1767R, 2SA1972, KSA1625-K, KSA1625-L, KTA1277, KTA1277O or KTA1277Y.