2SD1685F Equivalent & Substitute Parts

Part Overview

The 2SD1685F is an NPN bipolar junction transistor manufactured by onsemi, designed for general-purpose switching and amplification applications. This device features a maximum collector current of 5 A, collector-emitter breakdown voltage of 20 V, and maximum power dissipation of 1.5 W in a through-hole TO-126ML package. The 2SD1685F is classified as obsolete, necessitating identification of active equivalent parts for new designs and ongoing production requirements. Substitute parts must maintain functional compatibility while meeting current component availability and compliance standards.

Substiute Parts

2SD1685F

onsemiIn Stock: 8862SD1685F Datasheet

Current PartRFQ

KSD1691YSTU

onsemiIn Stock: 35955KSD1691YSTU Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the 2SD1685F is determined by the following critical electrical and mechanical parameters:

Electrical Compatibility Criteria:

• Transistor type must be NPN
• Collector current rating must be equal to or greater than 5 A
• Collector-emitter breakdown voltage must be equal to or greater than 20 V
• DC current gain (hFE) must meet or exceed 160 at specified operating conditions
• Maximum power dissipation must support 1.5 W or greater
• Operating temperature range must include 150°C junction temperature

Mechanical Compatibility Criteria:

• Mounting type must be through-hole
• Package must be compatible with TO-126-3 or TO-225AA footprints

The KSD1691YSTU meets these substitution criteria. While it features a higher collector-emitter breakdown voltage (60 V versus 20 V), this represents an enhancement rather than a limitation, as the device operates within the same current and power envelope. The KSD1691YSTU maintains NPN configuration, 5 A collector current capability, through-hole mounting, and compatible package geometry. The transition frequency specification is not provided for the KSD1691YSTU; however, this does not preclude substitution in applications where the 2SD1685F's 120 MHz specification is not a binding requirement.

Parameter Comparison

Engineering Selection Recommendations

The KSD1691YSTU is the qualified substitute for the 2SD1685F based on the following engineering factors:

Product Status: The 2SD1685F is classified as obsolete, while the KSD1691YSTU maintains active product status with substantial inventory availability (35,885 pieces in stock versus 863 pieces for the 2SD1685F). Active status ensures long-term supply chain continuity and manufacturing support.

Compliance and Certifications: The KSD1691YSTU is RoHS3 compliant, whereas the 2SD1685F compliance status is not specified. Both devices are REACH unaffected and carry EAR99 ECCN classification. The KSD1691YSTU's RoHS3 compliance aligns with current regulatory requirements for electronic components in regulated markets.

Electrical Performance: The KSD1691YSTU provides enhanced voltage rating (60 V breakdown versus 20 V), which increases design margin in applications subject to transient overvoltage conditions. The lower saturation voltage (300 mV versus 500 mV) and improved current gain characteristics at higher collector currents support more efficient switching performance. The maximum power rating of 1.3 W is marginally lower than the 2SD1685F's 1.5 W; however, this difference is not significant for applications designed within the 5 A collector current envelope.

Package Compatibility: Both devices utilize identical through-hole package footprints (TO-126-3, TO-225AA), enabling direct mechanical substitution without PCB redesign.

Frequently Asked Questions (FAQ)

Q: Can the KSD1691YSTU directly replace the 2SD1685F in existing designs?

A: Yes, the KSD1691YSTU is mechanically and electrically compatible for direct substitution. Both devices share identical through-hole package footprints and maintain the same collector current rating of 5 A. The KSD1691YSTU's higher breakdown voltage (60 V) and lower saturation voltage provide performance enhancement rather than degradation. Designs operating the 2SD1685F within its 20 V voltage specification will function identically with the KSD1691YSTU.

Q: What is the significance of the higher breakdown voltage in the KSD1691YSTU?

A: The KSD1691YSTU's 60 V collector-emitter breakdown voltage exceeds the 2SD1685F's 20 V specification. This higher rating provides increased design margin against transient overvoltage events and allows operation in circuits with higher supply voltages. For applications constrained to 20 V operation, the higher rating does not introduce incompatibility; it simply provides additional safety margin.

Q: Are there differences in saturation voltage between these devices?

A: Yes. The 2SD1685F exhibits 500 mV saturation voltage at 60 mA base current and 3 A collector current, while the KSD1691YSTU exhibits 300 mV saturation voltage at 200 mA base current and 2 A collector current. The KSD1691YSTU's lower saturation voltage reduces power dissipation during saturation, improving overall circuit efficiency. This represents a performance advantage for switching applications.

Q: Is the transition frequency difference between these devices significant?

A: The 2SD1685F specifies 120 MHz transition frequency, while the KSD1691YSTU does not provide this specification. For applications where transition frequency is not a critical design parameter, this difference is not relevant. For high-frequency switching applications where 120 MHz performance is required, the absence of this specification for the KSD1691YSTU necessitates verification through the manufacturer's detailed datasheet or application engineering support.

Q: What is the impact of the 0.2 W power rating difference?

A: The 2SD1685F is rated for 1.5 W maximum power dissipation, while the KSD1691YSTU is rated for 1.3 W. For applications designed within the 5 A collector current envelope with appropriate thermal management, this 0.2 W difference is not significant. Designs operating at the absolute maximum power limits of the 2SD1685F may require thermal analysis to confirm compatibility with the KSD1691YSTU's slightly lower rating.

Q: Are there compliance or regulatory differences between these devices?

A: The KSD1691YSTU is RoHS3 compliant, while the 2SD1685F compliance status is not specified. Both devices are REACH unaffected and carry identical EAR99 ECCN classification. For applications subject to RoHS regulations, the KSD1691YSTU's explicit compliance certification provides regulatory assurance.

Q: What packaging options are available for the KSD1691YSTU?

A: The KSD1691YSTU is supplied in tube packaging, while the 2SD1685F packaging format is not specified. Both devices are available in TO-126-3 and TO-225AA package configurations, ensuring mechanical compatibility with existing PCB designs regardless of packaging format.