BS170G N-Channel MOSFET Equivalent & Substitute Parts

Part Overview

The BS170G is an N-Channel MOSFET manufactured by onsemi, rated for 60V drain-to-source voltage with 500mA continuous drain current in a TO-92-3 through-hole package. This device is classified as obsolete, making equivalent substitute parts necessary for ongoing production and maintenance applications. The BS170G serves as a small-signal switching transistor suitable for low-power digital and analog circuit applications requiring through-hole mounting.

Key Parameters

Parameter	Value	Unit
FET Type	N-Channel	—
Technology	MOSFET (Metal Oxide)	—
Drain to Source Voltage (Vdss)	60	V
Continuous Drain Current (Id) @ 25°C	500	mA
Drive Voltage (Max Rds On)	10	V
Rds On (Max) @ 200mA, 10V	5	Ohm
Vgs(th) (Max) @ 1mA	3	V
Vgs (Max)	±20	V
Input Capacitance (Ciss) @ 10V	60	pF
Power Dissipation (Max)	350	mW
Operating Temperature Range	-55 to 150	°C
Mounting Type	Through Hole	—
Package	TO-92-3 (TO-226-3)	—

Substitute Part Grouping Explanation

Substitution of the BS170G is determined by electrical and mechanical parameter equivalence across the following criteria:

Electrical Equivalence Requirements:

Drain-to-source voltage (Vdss) must equal 60V
Continuous drain current (Id) must equal 500mA at 25°C
Gate-source threshold voltage (Vgs(th)) must equal 3V at 1mA
Maximum gate-source voltage (Vgs) must equal ±20V
On-state resistance (Rds On) must equal 5 Ohm at 200mA, 10V
Drive voltage (Max Rds On) must equal 10V
Operating temperature range must span -55°C to 150°C

Mechanical Equivalence Requirements:

FET type must be N-Channel
Technology must be MOSFET (Metal Oxide)
Mounting type must be Through Hole
Package must be TO-92-3 or TO-226-3 compatible

All substitute parts listed maintain identical electrical specifications and through-hole package compatibility with the BS170G, ensuring direct functional replacement in existing circuit designs.

Parameter Comparison

Parameter	BS170G (onsemi)	BS170-D26Z (Fairchild)	BS170-D27Z (onsemi)	BS170-D74Z (onsemi)
Manufacturer	onsemi	Fairchild Semiconductor	onsemi	onsemi
Product Status	Obsolete	Active	Active	Obsolete
FET Type	N-Channel	N-Channel	N-Channel	N-Channel
Vdss	60V	60V	60V	60V
Id @ 25°C	500mA	500mA	500mA	500mA
Rds On (Max) @ 200mA, 10V	5 Ohm	5 Ohm	5 Ohm	5 Ohm
Vgs(th) (Max) @ 1mA	3V	3V	3V	3V
Vgs (Max)	±20V	±20V	±20V	±20V
Ciss (Max) @ 10V	60 pF	40 pF	40 pF	40 pF
Power Dissipation (Max)	350mW	830mW	830mW	830mW
Operating Temperature	-55 to 150°C	-55 to 150°C	-55 to 150°C	-55 to 150°C
Package	TO-92-3	TO-92-3	TO-92-3	TO-92-3
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
REACH Status	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected

Engineering Selection Recommendations

BS170-D27Z (onsemi) — Recommended Primary Substitute

The BS170-D27Z is the preferred substitute for the obsolete BS170G. Both devices are manufactured by onsemi and share identical electrical specifications. The BS170-D27Z carries Active product status, ensuring continued availability and supply chain reliability. This part is ROHS3 compliant and REACH unaffected, meeting current environmental and regulatory requirements. The BS170-D27Z is supplied in Cut Tape (CT) packaging with 3,587 units in stock.

BS170-D26Z (Fairchild Semiconductor) — Secondary Substitute

The BS170-D26Z manufactured by Fairchild Semiconductor provides an alternative substitute with Active product status. All core electrical parameters match the BS170G specification. This part is ROHS3 compliant and REACH unaffected. The BS170-D26Z is supplied in Bulk packaging with 5,420 units in stock. Cross-manufacturer substitution is electrically valid based on parameter equivalence.

BS170-D74Z (onsemi) — Tertiary Substitute

The BS170-D74Z is an onsemi-manufactured substitute with identical electrical specifications to the BS170G. However, this part carries Obsolete product status, limiting its suitability for new designs or long-term production applications. The BS170-D74Z is ROHS3 compliant and REACH unaffected, with 22,347 units currently in stock. This part is suitable only for legacy system maintenance where supply continuity is not a primary concern.

Power Dissipation Consideration

All substitute parts (BS170-D26Z, BS170-D27Z, BS170-D74Z) feature 830mW maximum power dissipation, compared to the BS170G specification of 350mW. This represents a 2.37× increase in thermal capability. Circuits designed within the BS170G 350mW thermal envelope operate with additional thermal margin when using substitute parts, improving reliability and reducing thermal stress.

Frequently Asked Questions (FAQ)

Q: Can the BS170-D27Z directly replace the BS170G in existing circuit boards?

A: Yes. The BS170-D27Z is electrically and mechanically equivalent to the BS170G. Both devices feature identical Vdss (60V), Id (500mA), Rds On (5 Ohm), and TO-92-3 through-hole package specifications. No circuit modifications are required for direct substitution.

Q: What is the difference between the BS170G and BS170-D27Z?

A: The primary differences are product status and power dissipation rating. The BS170G is obsolete with 350mW maximum power dissipation. The BS170-D27Z is active with 830mW maximum power dissipation. Input capacitance (Ciss) differs slightly: BS170G at 60 pF versus BS170-D27Z at 40 pF. All other electrical parameters are identical.

Q: Why do the substitute parts have higher power dissipation ratings?

A: The substitute parts (BS170-D26Z, BS170-D27Z, BS170-D74Z) are rated for 830mW maximum power dissipation compared to the BS170G at 350mW. This reflects improved thermal design or different manufacturing processes. Circuits operating within the original 350mW specification benefit from increased thermal margin when using substitute parts.

Q: Is the BS170-D26Z from Fairchild Semiconductor compatible with the BS170G?

A: Yes. The BS170-D26Z is electrically equivalent to the BS170G across all specified parameters: Vdss, Id, Rds On, Vgs(th), and operating temperature range. Cross-manufacturer substitution is valid based on electrical parameter equivalence. The BS170-D26Z is ROHS3 compliant and REACH unaffected.

Q: Which substitute part should be selected for new production designs?

A: The BS170-D27Z (onsemi) is the recommended choice for new production designs. This part carries Active product status, ensuring long-term supply availability. It is ROHS3 compliant, REACH unaffected, and manufactured by the same company as the original BS170G, providing design continuity and supply chain stability.

Q: Are there packaging differences between the BS170G and substitute parts?

A: All parts use the TO-92-3 (TO-226-3) through-hole package. The BS170-D27Z and BS170-D74Z feature formed leads (TO-226AA), while the BS170-D26Z also features formed leads. These variations are compatible with standard TO-92-3 footprints and do not affect circuit board assembly or functionality.

Q: What is the significance of the lower input capacitance in substitute parts?

A: The substitute parts feature 40 pF input capacitance (Ciss) compared to the BS170G at 60 pF. Lower input capacitance reduces gate charge requirements and improves switching speed characteristics. This represents an improvement over the original specification and does not create compatibility issues in existing circuit designs.

Q: Can the BS170-D74Z be used in new designs despite its obsolete status?

A: The BS170-D74Z is electrically equivalent to the BS170G and is currently in stock with 22,347 units available. However, its Obsolete product status indicates limited future availability. For new production designs requiring long-term supply assurance, the BS170-D27Z (Active status) is the preferred choice.

Q: What compliance certifications apply to the substitute parts?

A: All substitute parts (BS170-D26Z, BS170-D27Z, BS170-D74Z) are ROHS3 compliant and REACH unaffected. These certifications meet current environmental and regulatory requirements for electronic component manufacturing and use in the European Union and other regulated markets.

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