BSR56 JFET N-Channel Transistor: Equivalent & Substitute Parts

Part Overview

The BSR56 is an N-Channel JFET manufactured by onsemi, rated for 40 V breakdown voltage with 250 mW power dissipation in a surface mount SOT-23-3 package. This device is classified as obsolete, making substitute parts necessary for new designs and ongoing production requirements. The BSR56 serves applications requiring low-noise signal switching and amplification in compact form factors.

Substiute Parts

BSR56

onsemiIn Stock: 22859BSR56 Datasheet

Current PartRFQ

2SK545-11D-TB-E

onsemiIn Stock: 7142SK545-11D-TB-E Datasheet

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MMBF4391LT1G

onsemiIn Stock: 54550MMBF4391LT1G Datasheet

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2SK209-GR(TE85L,F)

Toshiba Semiconductor and StorageIn Stock: 22122SK209-GR(TE85L,F) Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the BSR56 is determined by the following critical parameters:

• Voltage Rating (V(BR)GSS): Substitute parts must meet or exceed 40 V to ensure safe operation in the original circuit.
• Drain Current (Idss): The BSR56 specifies 50 mA @ 15 V. Substitutes with comparable Idss ratings maintain similar gain and switching characteristics.
• Cutoff Voltage (VGS off): The 4 V specification at 0.5 nA defines the gate threshold behavior. Substitutes with similar VGS off values ensure predictable gate control.
• Power Dissipation (P-Max): The 250 mW rating establishes thermal limits. Substitutes must support equivalent or higher power ratings.
• Package Compatibility: All substitutes must use SOT-23-3 (SC-59, TO-236-3) surface mount packaging to ensure PCB compatibility.

Three substitute parts are identified based on these criteria, with variations in voltage rating, current handling, and product status.

Parameter Comparison

Engineering Selection Recommendations

MMBF4391LT1G is the primary substitute for new designs. This part maintains the same Idss specification (50 mA @ 15 V) and VGS off threshold (4 V @ 10 nA) as the BSR56, ensuring functional equivalence. The MMBF4391LT1G carries Active product status, guaranteeing long-term availability and supply chain stability. It is ROHS3 compliant and MSL 1 rated. The 30 V voltage rating is lower than the BSR56's 40 V specification; applications operating above 30 V require voltage margin verification.

2SK209-GR(TE85L,F) provides an alternative with higher voltage rating (50 V) and Active product status. This Toshiba device offers superior voltage headroom for designs with transient overvoltage conditions. The 14 mA Idss specification differs from the BSR56, affecting gain characteristics. The 150 mW power rating is lower than the BSR56's 250 mW specification.

2SK545-11D-TB-E matches the 40 V voltage rating and SOT-23-3 package of the BSR56 but carries Obsolete product status. The 60 µA Idss specification is significantly lower than the BSR56's 50 mA, making this part unsuitable for applications requiring high drain current. This substitute is not recommended for new designs.

Frequently Asked Questions (FAQ)

Q: Can MMBF4391LT1G replace BSR56 in all applications?

A: MMBF4391LT1G is functionally equivalent for applications operating at or below 30 V. The matching Idss (50 mA @ 15 V) and VGS off (4 V) specifications ensure identical switching and amplification behavior. Applications designed for the BSR56's 40 V rating require circuit analysis to confirm 30 V operation is acceptable.

Q: Why is 2SK545-11D-TB-E listed as a substitute if it has lower Idss?

A: 2SK545-11D-TB-E is included in the substitute list based on package compatibility and voltage rating alignment. However, the 60 µA Idss specification is substantially lower than the BSR56's 50 mA, making it unsuitable for most applications. This part is not recommended for new designs due to its Obsolete status and incompatible current characteristics.

Q: What is the difference between SOT-23-3 and SC-59 packaging?

A: SOT-23-3 and SC-59 are equivalent designations for the same three-lead surface mount package. Both terms refer to the same physical form factor and pin configuration. The 2SK209-GR(TE85L,F) uses the SC-59 designation but is mechanically and electrically compatible with SOT-23-3 footprints.

Q: Is 2SK209-GR(TE85L,F) suitable for high-voltage applications?

A: Yes, 2SK209-GR(TE85L,F) offers the highest voltage rating at 50 V, providing additional margin above the BSR56's 40 V specification. However, the 14 mA Idss differs from the BSR56's 50 mA, and the 150 mW power rating is lower than the BSR56's 250 mW. Circuit verification is required to confirm compatibility with the original design.

Q: Are all substitutes RoHS3 compliant?

A: Yes, all listed substitutes (MMBF4391LT1G, 2SK545-11D-TB-E, and 2SK209-GR(TE85L,F)) are ROHS3 compliant with MSL 1 (Unlimited) moisture sensitivity rating, matching the BSR56's environmental compliance profile.