BF256C

Overview

The onsemi BF256C is an N-channel RF JFET transistor designed for VHF/UHF amplifier applications. It operates within a drain-gate voltage of 30V and a gate-source voltage of -30V, with a total device dissipation of 350mW at 25°C. The zero-gate voltage drain current (IDSS) ranges from 11mA to 18mA under test conditions of VGS=0V and VGS=15V. Common source forward transconductance (gfs) is specified at 4.5 mmhos at 1KHz. The component utilizes a TO-92-3 package and supports an operating temperature range from -55°C to 150°C.

Feature Summary

• Engineered specifically for VHF and UHF amplifier circuits
• Utilizes a standard TO-92 three-pin through-hole package
• Provides stable small-signal performance with defined transconductance characteristics

Applications

• VHF amplifiers
• UHF amplifiers
• RF signal processing stages

Procurement Notes

Verify the obsolete status of this component before integration into new designs. Confirm availability of equivalent replacement parts such as the MMBF5485 if production continuity is required. Ensure that any substitute maintains compatibility with existing circuit parameters and physical footprint constraints.

Selection Notes

Select this component based on its specific IDSS range of 11mA to 18mA and its suitability for high-frequency amplification tasks. Consider the thermal derating requirements above 25°C when designing the heat dissipation strategy. Verify that the TO-92 package dimensions align with the target PCB layout specifications.

Part Context

The BF256C belongs to the BF256 family, which includes variants A and B differentiated primarily by their IDSS current bins. This specific model represents the highest current bin within the series. The datasheet indicates sourcing from process 50, reflecting specific manufacturing lineage distinct from other general-purpose JFETs.

Replacement Considerations

The MMBF5485 is documented as a similar replacement part. Verify pinout compatibility and electrical parameter overlap before substitution.