BCX71G Equivalent & Substitute Parts

Part Overview

The BCX71G is a PNP bipolar junction transistor manufactured by onsemi, housed in a SOT-23-3 surface mount package. This component is rated for 45 V collector-emitter breakdown voltage and 100 mA maximum collector current, with a maximum power dissipation of 350 mW. The BCX71G is classified as obsolete, making identification of functionally equivalent active alternatives necessary for new designs and ongoing production support. Substitute parts must maintain electrical compatibility within the specified parameter ranges while offering active product status and current manufacturing availability.

Key Parameters

Parameter	BCX71G Value	Unit
Transistor Type	PNP	—
Voltage - Collector Emitter Breakdown (Max)	45	V
Current - Collector (Ic) (Max)	100	mA
Power - Max	350	mW
Vce Saturation (Max) @ Ib, Ic	550mV @ 1.25mA, 50mA	—
Current - Collector Cutoff (Max)	20	nA
DC Current Gain (hFE) (Min) @ Ic, Vce	120 @ 2mA, 5V	—
Package / Case	SOT-23-3 (TO-236)	—
Mounting Type	Surface Mount	—
Product Status	Obsolete	—

Substitute Part Grouping Explanation

Substitution of the BCX71G is determined by strict adherence to the following electrical and mechanical parameters:

Critical Matching Parameters:

Transistor Type: PNP (required)
Voltage - Collector Emitter Breakdown (Max): 45 V or greater
Current - Collector (Ic) (Max): 100 mA or greater
Package / Case: SOT-23-3 (TO-236) (required for mechanical compatibility)
Mounting Type: Surface Mount (required)

Acceptable Variation Parameters:

Power - Max: 225 mW or greater (BCX71G rated at 350 mW; lower ratings acceptable if other parameters met)
Vce Saturation: Variations acceptable within application requirements
DC Current Gain (hFE): Variations acceptable; minimum 100 at specified test conditions
Current - Collector Cutoff: Variations acceptable

Substitute parts are grouped into two categories:

Category A - Direct Electrical Equivalents (100 mA, 45 V): BC857ALT1G, BC857BLT1G, BC857BLT3G, BC857CLT1G, BC857CLT3G, BCW70LT1G, NSVBC857BLT3G

These parts maintain the 100 mA collector current rating and 45 V breakdown voltage of the BCX71G. All are active products with current manufacturing status and RoHS3 compliance.

Category B - Higher Current Capability (exceeds 100 mA, 45 V): BC807-16LT1G (500 mA), BCW68GLT1G (800 mA)

These parts exceed the BCX71G current rating while maintaining or exceeding the 45 V breakdown voltage. Suitable for applications requiring higher current capacity within the same voltage class.

Category C - Lower Voltage Rating (100 mA, 40 V): MMBT3906LT1G (40 V, 200 mA)

This part operates at reduced breakdown voltage (40 V vs. 45 V) but provides higher current capacity. Suitable only for applications with maximum operating voltages below 40 V.

Parameter Comparison

Part Number	Manufacturer	Transistor Type	Ic (Max) mA	Vce Breakdown (Max) V	Power (Max) mW	Package	Product Status	RoHS Status
BCX71G	onsemi	PNP	100	45	350	SOT-23-3	Obsolete	REACH Unaffected
BC807-16LT1G	onsemi	PNP	500	45	300	SOT-23-3	Active	ROHS3 Compliant
BC857ALT1G	onsemi	PNP	100	45	300	SOT-23-3	Active	ROHS3 Compliant
BC857BLT1G	onsemi	PNP	100	45	300	SOT-23-3	Active	ROHS3 Compliant
BC857BLT3G	onsemi	PNP	100	45	300	SOT-23-3	Active	ROHS3 Compliant
BC857CLT1G	onsemi	PNP	100	45	300	SOT-23-3	Active	ROHS3 Compliant
BC857CLT3G	onsemi	PNP	100	45	300	SOT-23-3	Active	ROHS3 Compliant
BCW68GLT1G	onsemi	PNP	800	45	225	SOT-23-3	Active	ROHS3 Compliant
BCW70LT1G	onsemi	PNP	100	45	225	SOT-23-3	Active	ROHS3 Compliant
MMBT3906LT1G	onsemi	PNP	200	40	300	SOT-23-3	Active	ROHS3 Compliant
NSVBC857BLT3G	onsemi	PNP	100	45	225	SOT-23-3	Active	ROHS3 Compliant

Engineering Selection Recommendations

Primary Substitutes (Direct Equivalents):

BC857ALT1G, BC857BLT1G, BC857BLT3G, BC857CLT1G, BC857CLT3G, and BCW70LT1G are recommended as primary substitutes for the BCX71G. These parts maintain identical collector current (100 mA) and breakdown voltage (45 V) specifications. All are active products with RoHS3 compliance and current manufacturing status. The BC857 series variants differ in DC current gain (hFE) specifications: BC857A (125 @ 2mA, 5V), BC857B (220 @ 2mA, 5V), and BC857C (420 @ 2mA, 5V). Selection among these variants depends on application requirements for current gain. Packaging options include Cut Tape (CT) and Tape & Reel (TR) formats.

Secondary Substitutes (Higher Current Capability):

BC807-16LT1G and BCW68GLT1G provide higher collector current ratings (500 mA and 800 mA respectively) while maintaining 45 V breakdown voltage. These are suitable for applications requiring current capacity beyond the BCX71G specification. Both are active products with RoHS3 compliance.

Conditional Substitute (Lower Voltage Rating):

MMBT3906LT1G operates at 40 V breakdown voltage with 200 mA collector current. This part is suitable only for applications with maximum operating voltages not exceeding 40 V. It is an active product with RoHS3 compliance and higher transition frequency (250 MHz).

Compliance Considerations:

All recommended substitutes are RoHS3 compliant and REACH unaffected, meeting current regulatory requirements. The BCX71G is classified as REACH unaffected; substitute parts maintain this status. All substitute parts are manufactured by onsemi and housed in SOT-23-3 packages, ensuring mechanical and thermal compatibility.

Frequently Asked Questions (FAQ)

Q: Can BC857ALT1G directly replace BCX71G in all applications?

A: BC857ALT1G meets all critical electrical parameters of the BCX71G: 100 mA collector current, 45 V breakdown voltage, and SOT-23-3 package. The primary difference is product status (active vs. obsolete) and RoHS3 compliance. Electrical performance is equivalent within specified parameter ranges.

Q: What is the difference between BC857A, BC857B, and BC857C variants?

A: These variants differ in DC current gain (hFE) specifications. BC857A has minimum hFE of 125 at 2 mA, 5V; BC857B has 220; BC857C has 420. All maintain identical voltage and current ratings. Selection depends on application requirements for current gain characteristics.

Q: Can I use BC807-16LT1G as a direct replacement for BCX71G?

A: BC807-16LT1G is electrically compatible with higher current capability (500 mA vs. 100 mA) and identical 45 V breakdown voltage. It is suitable for applications where the BCX71G is used but higher current capacity is beneficial or required. The lower power rating (300 mW vs. 350 mW) is acceptable for most applications operating within 100 mA.

Q: Is MMBT3906LT1G suitable for BCX71G replacement?

A: MMBT3906LT1G is suitable only for applications with maximum operating voltages below 40 V. It provides higher collector current (200 mA) and transition frequency (250 MHz) but operates at reduced breakdown voltage (40 V vs. 45 V). Verify application voltage requirements before substitution.

Q: What packaging options are available for BC857 substitutes?

A: BC857 variants are available in Cut Tape (CT) and Digi-Reel format (BC857ALT1G, BC857BLT1G, BC857CLT1G) and Tape & Reel (TR) format (BC857BLT3G, BC857CLT3G). Selection depends on procurement and assembly requirements. All maintain identical electrical specifications.

Q: Are all substitute parts RoHS3 compliant?

A: All recommended substitute parts are RoHS3 compliant. The BCX71G is classified as REACH unaffected; all substitutes maintain this status. Compliance documentation is available from onsemi for regulatory verification.

Q: What is the inventory status of substitute parts?

A: All recommended substitutes are active products with current manufacturing status and substantial inventory availability. BC857ALT1G has the highest inventory (747,693 pcs), followed by MMBT3906LT1G (608,935 pcs) and BC807-16LT1G (146,930 pcs). Inventory levels support both new design implementation and production volume requirements.

Q: Can I mix different BC857 variants in the same circuit?

A: BC857A, BC857B, and BC857C variants are electrically interchangeable within the same circuit provided application requirements accommodate the range of current gain values (125 to 420). Verify circuit design tolerances for current gain variation before mixing variants.

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