BF244B Equivalent & Substitute Parts

Part Overview

The BF244B is an RF MOSFET JFET transistor manufactured by onsemi, designed for RF applications operating at 100MHz with a 15V test voltage rating. The device is packaged in a TO-92-3 through-hole configuration and features a noise figure of 1.5dB with a 50mA current rating. The BF244B is classified as obsolete, making identification of suitable substitute components necessary for ongoing design support, maintenance, and new production applications where through-hole or surface-mount alternatives are acceptable.

Substiute Parts

BF244B

onsemiIn Stock: 3337BF244B Datasheet

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MMBF5485

onsemiIn Stock: 65234MMBF5485 Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the BF244B is determined by the following critical parameters:

Technology & Configuration: Both the main part and substitute must be N-Channel JFET devices to maintain functional equivalence in RF circuit applications.

Voltage Ratings: The substitute must support the test voltage of 15V and rated voltage of 30V to ensure safe operation within the original circuit design envelope.

Frequency Performance: The substitute must operate at or above 100MHz to support RF applications without performance degradation.

Current Handling: The substitute must accommodate the 50mA current requirement of the original design.

Noise Figure: The substitute noise figure specification must be compatible with the RF application requirements.

Package Compatibility: Substitutes may differ in mounting type (through-hole versus surface-mount) and package form factor, provided the electrical parameters remain within acceptable ranges for the application.

The MMBF5485 qualifies as a substitute based on matching technology (N-Channel JFET), voltage ratings (15V test, 25V rated), and frequency capability (400MHz, exceeding the 100MHz requirement). The primary trade-offs are reduced current rating (10mA versus 50mA) and increased noise figure (4dB versus 1.5dB), along with a change from through-hole to surface-mount packaging.

Parameter Comparison

Engineering Selection Recommendations

Product Status Consideration: The BF244B is classified as obsolete, while the MMBF5485 maintains active product status with current manufacturing support and availability. Selection of the MMBF5485 ensures access to ongoing supply and technical documentation.

Compliance & Certifications: The MMBF5485 is ROHS3 compliant, meeting modern environmental and regulatory requirements. Both devices maintain REACH Unaffected status and unlimited moisture sensitivity classification, indicating equivalent handling and storage requirements.

Electrical Parameter Trade-offs: The MMBF5485 provides superior frequency performance (400MHz versus 100MHz), supporting higher-speed RF applications. However, the reduced current rating (10mA versus 50mA) and increased noise figure (4dB versus 1.5dB) require circuit-level evaluation to confirm suitability for applications originally designed around the BF244B specifications.

Packaging & Manufacturing Impact: The transition from TO-92-3 through-hole to SOT-23-3 surface-mount packaging necessitates PCB redesign and assembly process modification. This change is appropriate for new production designs but may require alternative solutions for through-hole retrofit applications.

Frequently Asked Questions (FAQ)

Q: Can the MMBF5485 directly replace the BF244B in existing through-hole PCB designs?

A: No. The MMBF5485 uses SOT-23-3 surface-mount packaging, while the BF244B uses TO-92-3 through-hole packaging. Direct PCB substitution is not possible without board redesign. Through-hole adapter solutions or alternative through-hole JFET devices may be required for retrofit applications.

Q: What are the critical electrical differences between these devices?

A: The MMBF5485 operates at higher frequency (400MHz versus 100MHz) and provides superior frequency performance. However, it has reduced current handling capacity (10mA versus 50mA) and higher noise figure (4dB versus 1.5dB). Applications requiring the full 50mA current rating or 1.5dB noise figure specification cannot use the MMBF5485 as a substitute.

Q: Are both devices suitable for RF applications?

A: Yes. Both are N-Channel JFET devices designed for RF applications. The BF244B operates at 100MHz, while the MMBF5485 extends to 400MHz. The choice depends on the specific frequency requirements and current/noise specifications of the target application.

Q: What is the voltage compatibility between these devices?

A: Both devices support 15V test voltage. The BF244B has a 30V rated voltage, while the MMBF5485 has a 25V rated voltage. Applications operating near the 30V maximum should be evaluated to confirm the MMBF5485 provides adequate voltage margin.

Q: Does the MMBF5485 meet modern compliance requirements?

A: Yes. The MMBF5485 is ROHS3 compliant and maintains REACH Unaffected status. The BF244B, being obsolete, may not meet current environmental compliance standards for new production designs.

Q: What inventory considerations apply to these devices?

A: The BF244B has 3,240 pieces in stock but is obsolete with no ongoing manufacturing. The MMBF5485 has 65,200 pieces in stock and maintains active product status, ensuring long-term availability for production and support applications.