BCX70J Equivalent & Substitute Parts

Part Overview

The BCX70J is an NPN bipolar junction transistor manufactured by onsemi, housed in a SOT-23-3 surface mount package. This device is rated for 45 V collector-emitter breakdown voltage with a maximum collector current of 200 mA and 350 mW power dissipation. The BCX70J operates at a transition frequency of 125 MHz and features a minimum DC current gain of 250 at 2 mA collector current and 5 V collector-emitter voltage.

The BCX70J is classified as obsolete. Identifying equivalent and substitute parts is necessary to support ongoing design requirements, system maintenance, and production continuity where this component is specified in existing applications.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	45	V
Current - Collector (Ic) (Max)	200	mA
Power - Max	350	mW
Frequency - Transition	125	MHz
DC Current Gain (hFE) (Min) @ Ic, Vce	250 @ 2mA, 5V	—
Vce Saturation (Max) @ Ib, Ic	550mV @ 1.25mA, 50mA	—
Package / Case	SOT-23-3	—
Mounting Type	Surface Mount	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the BCX70J is determined by electrical and mechanical compatibility across the following critical parameters:

Voltage Rating: All substitute parts maintain the 45 V collector-emitter breakdown voltage specification, ensuring compatibility with circuit voltage constraints.

Package Compatibility: All substitute parts use the SOT-23-3 (TO-236-3, SC-59) surface mount package, providing mechanical and thermal compatibility with existing PCB layouts and assembly processes.

Transistor Type: All substitutes are NPN bipolar junction transistors, maintaining functional equivalence in circuit topology and biasing requirements.

Current and Power Ratings: Substitute parts are grouped into two categories based on maximum collector current:

Higher Current Capability (500 mA): BC817 series variants (BC817-16LT1G, BC817-16LT3G, BC817-25LT1G, BC817-25LT3G, BC817-40LT1G, BC817-40LT3G) provide 500 mA maximum collector current, exceeding the BCX70J specification of 200 mA. These parts operate at 300 mW maximum power dissipation.
Lower Current Capability (100 mA): BC847 series variants (BC847ALT1G, BC847BLT1G, BC847BLT3G, BC847CLT1G) provide 100 mA maximum collector current, which is below the BCX70J specification of 200 mA. These parts operate at 300 mW maximum power dissipation.

DC Current Gain (hFE): Substitute parts are available with minimum hFE values of 100, 160, or 250 at specified test conditions, allowing selection based on circuit gain requirements.

Frequency Response: BC817 and BC847 series parts operate at 100 MHz transition frequency, compared to the BCX70J specification of 125 MHz.

Product Status: All substitute parts are classified as Active, ensuring ongoing availability and manufacturing support.

Parameter Comparison

Parameter	BCX70J	BC817-16LT1G	BC817-25LT1G	BC817-40LT1G	BC847ALT1G	BC847BLT1G	BC847CLT1G
Transistor Type	NPN	NPN	NPN	NPN	NPN	NPN	NPN
Voltage - Collector Emitter Breakdown (Max)	45 V	45 V	45 V	45 V	45 V	45 V	45 V
Current - Collector (Ic) (Max)	200 mA	500 mA	500 mA	500 mA	100 mA	100 mA	100 mA
Power - Max	350 mW	300 mW	300 mW	300 mW	300 mW	300 mW	300 mW
Frequency - Transition	125 MHz	100 MHz	100 MHz	100 MHz	100 MHz	100 MHz	100 MHz
DC Current Gain (hFE) (Min) @ Ic, Vce	250 @ 2mA, 5V	100 @ 100mA, 1V	160 @ 100mA, 1V	250 @ 100mA, 1V	110 @ 2mA, 5V	200 @ 2mA, 5V	420 @ 2mA, 5V
Vce Saturation (Max) @ Ib, Ic	550mV @ 1.25mA, 50mA	700mV @ 50mA, 500mA	700mV @ 50mA, 500mA	700mV @ 50mA, 500mA	600mV @ 5mA, 100mA	600mV @ 5mA, 100mA	600mV @ 5mA, 100mA
Package / Case	SOT-23-3	SOT-23-3	SOT-23-3	SOT-23-3	SOT-23-3	SOT-23-3	SOT-23-3
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Product Status	Obsolete	Active	Active	Active	Active	Active	Active
RoHS Status	—	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

For Applications Requiring Maximum Collector Current ≤ 200 mA:

The BC817-40LT1G and BC817-40LT3G are the primary substitutes. These parts provide 500 mA maximum collector current, which exceeds the BCX70J specification, and feature a minimum DC current gain of 250 at 100 mA and 1 V, matching the BCX70J gain specification at different test conditions. Both variants are Active products with ROHS3 compliance. The BC817-40LT1G is supplied in Cut Tape (CT) & Digi-Reel® packaging, while the BC817-40LT3G is supplied in Tape & Reel (TR) packaging. Selection between these variants depends on procurement and assembly requirements.

The BC817-25LT1G and BC817-25LT3G provide 500 mA maximum collector current with a minimum DC current gain of 160 at 100 mA and 1 V. These parts are suitable for applications where the lower gain specification is acceptable. Both are Active products with ROHS3 compliance.

The BC817-16LT1G and BC817-16LT3G provide 500 mA maximum collector current with a minimum DC current gain of 100 at 100 mA and 1 V. These parts are suitable for applications where lower gain is acceptable or where higher base drive is available.

For Applications Requiring Lower Collector Current (≤ 100 mA):

The BC847CLT1G is the primary substitute for low-current applications. This part provides 100 mA maximum collector current and features a minimum DC current gain of 420 at 2 mA and 5 V, exceeding the BCX70J specification. The BC847CLT1G is an Active product with ROHS3 compliance.

The BC847BLT1G and BC847BLT3G provide 100 mA maximum collector current with a minimum DC current gain of 200 at 2 mA and 5 V. Both are Active products with ROHS3 compliance. The BC847BLT1G is supplied in Cut Tape (CT) & Digi-Reel® packaging, while the BC847BLT3G is supplied in Tape & Reel (TR) packaging.

The BC847ALT1G provides 100 mA maximum collector current with a minimum DC current gain of 110 at 2 mA and 5 V. This part is suitable for applications where lower gain is acceptable. It is an Active product with ROHS3 compliance.

Compliance and Availability:

All substitute parts are ROHS3 compliant and classified as Active products, ensuring regulatory compliance and long-term manufacturing support. All parts maintain the SOT-23-3 surface mount package specification, providing direct mechanical compatibility with existing PCB designs.

Frequently Asked Questions (FAQ)

Q: Can BC817 series parts directly replace the BCX70J in all applications?

A: BC817 series parts are mechanically and electrically compatible with the BCX70J in applications where the collector current requirement does not exceed 200 mA. The BC817 series provides higher maximum collector current (500 mA) than the BCX70J (200 mA), making it suitable for applications operating within the BCX70J current specification. However, the transition frequency of BC817 parts (100 MHz) is lower than the BCX70J (125 MHz). Applications with stringent frequency requirements above 100 MHz should evaluate this difference.

Q: What is the difference between BC817-16, BC817-25, and BC817-40 variants?

A: These variants differ in their minimum DC current gain (hFE) specifications. The BC817-16 has a minimum hFE of 100, the BC817-25 has a minimum hFE of 160, and the BC817-40 has a minimum hFE of 250. Selection depends on the circuit's base drive availability and gain requirements. The BC817-40 matches the BCX70J minimum gain specification of 250.

Q: What is the difference between BC847A, BC847B, and BC847C variants?

A: These variants differ in their minimum DC current gain (hFE) specifications. The BC847A has a minimum hFE of 110, the BC847B has a minimum hFE of 200, and the BC847C has a minimum hFE of 420. The BC847C provides the highest gain and is suitable for applications requiring high current amplification with minimal base drive.

Q: Are the packaging variants (LT1G vs. LT3G) interchangeable?

A: The LT1G and LT3G designations indicate different packaging formats. LT1G denotes Cut Tape (CT) & Digi-Reel® packaging, while LT3G denotes Tape & Reel (TR) packaging. Both variants contain identical semiconductor dies and electrical specifications. Selection between these variants depends on procurement method and assembly equipment compatibility. They are not interchangeable in terms of packaging format but are electrically equivalent.

Q: Can BC847 series parts replace the BCX70J in high-current applications?

A: No. BC847 series parts are rated for a maximum collector current of 100 mA, which is below the BCX70J specification of 200 mA. BC847 parts are suitable only for applications where the collector current requirement does not exceed 100 mA. For applications requiring collector currents between 100 mA and 200 mA, BC817 series parts (500 mA maximum) are the appropriate substitute.

Q: What is the significance of the SOT-23-3 package specification?

A: The SOT-23-3 package (also designated TO-236-3 or SC-59) is a three-terminal surface mount package with standardized pin configuration and footprint. All substitute parts use this identical package, ensuring direct compatibility with existing PCB layouts, solder reflow profiles, and assembly processes. No PCB redesign is required when substituting between parts with the same SOT-23-3 package specification.

Q: Are all substitute parts RoHS compliant?

A: Yes. All substitute parts listed are ROHS3 compliant. The BCX70J product status does not specify RoHS compliance. All active substitute parts meet current RoHS directives, ensuring compliance with environmental and regulatory requirements for new designs and production.

Q: What is the operating temperature range difference between the BCX70J and substitute parts?

A: The BCX70J operating temperature specification is not provided in the available data. BC817 series parts operate from -65°C to 150°C (TJ), while BC847 series parts operate from -55°C to 150°C (TJ). Applications with temperature requirements outside these ranges require evaluation against specific circuit requirements.

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