BF421 Transistor TO-92 Plastic Case
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Prices updated: 12 Oct 2026
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About this product
The BF421 is a transistor supplied in a TO-92 plastic package, listed in the store as a PNP general-purpose device. Polarity should be verified against the datasheet, as the BF421 is widely documented as an NPN high-voltage transistor. It is used in general-purpose and video-output type circuits where a TO-92 device is needed.
Specifications
- Package
- TO-92 plastic
- Transistor type (per listing)
- PNP (verify on datasheet)
Frequently asked questions
How can I confirm the polarity of the BF421 before using it?
Read the part marking and look up the exact part number in the manufacturer's datasheet, which lists the transistor type. You can also check the transistor with a multimeter diode-test function: a good NPN or PNP junction shows a diode drop between base and emitter and between base and collector in the correct direction.
Can it be used as a direct replacement for a 2N-series general-purpose transistor?
Only after checking the datasheet. Polarity, voltage rating, current rating and pinout must match the circuit. Do not substitute without confirming these, especially the collector-emitter voltage rating.
