BC858ALT1 Equivalent & Substitute Parts

Part Overview

The BC858ALT1 is a PNP bipolar junction transistor manufactured by onsemi, rated for 30 V collector-emitter breakdown voltage and 100 mA maximum collector current in a surface mount SOT-23-3 package. This device is classified as obsolete, which necessitates identification of equivalent and substitute components for ongoing design support and procurement.

The BC858ALT1 operates across a temperature range of -55°C to 150°C and delivers 300 mW maximum power dissipation with a transition frequency of 100 MHz. The obsolete status of this part requires engineers to evaluate active alternatives that maintain electrical and mechanical compatibility with existing designs.

Key Parameters

Parameter	Value	Unit
Transistor Type	PNP	—
Voltage - Collector Emitter Breakdown (Max)	30	V
Current - Collector (Ic) (Max)	100	mA
Power - Max	300	mW
Frequency - Transition	100	MHz
Vce Saturation (Max) @ Ib, Ic	650 @ 5mA, 100mA	mV
DC Current Gain (hFE) (Min) @ Ic, Vce	125 @ 2mA, 5V	—
Operating Temperature	-55 to 150	°C
Mounting Type	Surface Mount	—
Package / Case	TO-236-3, SC-59, SOT-23-3	—

Substitute Part Grouping Explanation

Substitution of the BC858ALT1 is determined by the following critical parameters:

Electrical Compatibility Requirements:

Transistor type must be PNP
Collector-emitter breakdown voltage must be ≥ 30 V
Maximum collector current must be ≥ 100 mA
Maximum power dissipation must be ≥ 300 mW
Transition frequency must be ≥ 100 MHz
Vce saturation characteristics must be compatible with circuit bias conditions
DC current gain (hFE) must support required amplification

Mechanical Compatibility Requirements:

Mounting type must be surface mount
Package must be compatible with SOT-23-3 footprint (TO-236-3, SC-59, SOT-23-3)

Substitute parts are grouped into two categories:

Direct Equivalent: BC858ALT1G maintains identical electrical specifications and package format while offering active product status and RoHS3 compliance.

Functional Equivalents: Parts from Rohm Semiconductor (2SB1695 series, 2SB1706TL, 2SB1708TL, 2SB1710TL) and other manufacturers meet or exceed the electrical requirements but may feature enhanced performance characteristics (higher current ratings, increased power dissipation, or improved frequency response) while maintaining mechanical compatibility through equivalent or superior package specifications.

Parameter Comparison

Part Number	Manufacturer	Ic (Max) mA	Vce(br) V	Power mW	fT MHz	hFE @ Ic, Vce	Package	Status	RoHS
BC858ALT1	onsemi	100	30	300	100	125 @ 2mA, 5V	SOT-23-3	Obsolete	Non-compliant
BC858ALT1G	onsemi	100	30	300	100	125 @ 2mA, 5V	SOT-23-3	Active	ROHS3
2SB1695KT146	Rohm Semiconductor	1500	30	200	280	270 @ 100mA, 2V	SMT3	Active	ROHS3
2SB1695TL	Rohm Semiconductor	1500	30	500	280	270 @ 100mA, 2V	TSMT3	Active	ROHS3
2SB1706TL	Rohm Semiconductor	2000	30	500	280	270 @ 200mA, 2V	TSMT3	Active	ROHS3
2SB1708TL	Rohm Semiconductor	3000	30	500	200	270 @ 200mA, 2V	TSMT3	Active	ROHS3
2SB1710TL	Rohm Semiconductor	1000	30	500	320	270 @ 100mA, 2V	TSMT3	Active	ROHS3
BC857A,215	Nexperia USA Inc.	100	45	250	100	125 @ 2mA, 5V	TO-236AB	Active	ROHS3
BC858A RFG	Taiwan Semiconductor Corporation	100	30	200	100	125 @ 2mA, 5V	SOT-23	Active	ROHS3
BC858A-TP	Micro Commercial Co	100	30	200	100	125 @ 2mA, 5V	SOT-23-3	Active	—
BC858AE6327HTSA1	Infineon Technologies	100	30	330	250	125 @ 2mA, 5V	PG-SOT23	Last Time Buy	ROHS3

Engineering Selection Recommendations

Primary Recommendation: BC858ALT1G

The BC858ALT1G is the direct active equivalent of the BC858ALT1. This part maintains identical electrical specifications and package format while offering active product status and RoHS3 compliance. Selection of BC858ALT1G eliminates design modification requirements and provides the most straightforward transition path from the obsolete BC858ALT1.

Secondary Recommendations for Enhanced Performance:

The 2SB1710TL from Rohm Semiconductor provides a functional equivalent with superior transition frequency (320 MHz versus 100 MHz) and increased power dissipation (500 mW versus 300 mW) while maintaining the 30 V collector-emitter breakdown voltage and 100 mA minimum collector current capability. This part is suitable for designs requiring improved high-frequency performance.

The 2SB1695TL offers increased collector current capability (1.5 A) and power dissipation (500 mW) with enhanced transition frequency (280 MHz), appropriate for applications requiring higher current handling within the same voltage class.

Compliance Considerations:

BC858ALT1G, 2SB1695 series, 2SB1706TL, 2SB1708TL, 2SB1710TL, BC857A,215, and BC858A RFG all carry RoHS3 compliance certification. BC858A-TP does not specify RoHS status and requires verification before use in regulated applications.

BC857A,215 carries AEC-Q101 automotive qualification and is suitable for automotive-grade applications requiring enhanced reliability documentation.

Frequently Asked Questions (FAQ)

Q: Can BC858ALT1G be used as a direct replacement for BC858ALT1?

A: Yes. BC858ALT1G maintains identical electrical specifications (30 V Vce(br), 100 mA Ic, 300 mW power, 100 MHz fT) and package format (SOT-23-3). The primary difference is product status (active versus obsolete) and RoHS3 compliance. No circuit modifications are required.

Q: What is the difference between BC858ALT1G and 2SB1710TL?

A: Both are PNP transistors rated for 30 V with 100 mA minimum collector current. The 2SB1710TL features higher transition frequency (320 MHz versus 100 MHz), increased power dissipation (500 mW versus 300 mW), and higher DC current gain (270 versus 125). The 2SB1710TL uses a TSMT3 package rather than SOT-23-3, requiring PCB footprint verification before substitution.

Q: Are the Rohm 2SB1695 series parts compatible with the BC858ALT1 footprint?

A: The 2SB1695KT146 uses an SMT3 package, while 2SB1695TL uses TSMT3. Both differ from the SOT-23-3 footprint of BC858ALT1. PCB layout verification is required to confirm mechanical compatibility. The electrical specifications are compatible (30 V Vce(br), exceeding 100 mA Ic requirement).

Q: What is the significance of the operating temperature range difference between BC858ALT1 (-55°C to 150°C) and some substitutes?

A: BC858ALT1 specifies -55°C to 150°C operating range. Substitutes such as 2SB1695 series specify 150°C maximum junction temperature without explicit lower temperature limit. For applications requiring operation below 0°C, verify the substitute part's low-temperature specification against design requirements.

Q: Can BC857A,215 replace BC858ALT1?

A: BC857A,215 is electrically compatible (PNP, 100 mA Ic, 100 MHz fT, 125 hFE) but rated for 45 V Vce(br) versus 30 V. This higher voltage rating does not prevent substitution in 30 V circuits. The package is TO-236AB (compatible with SOT-23-3 footprint). BC857A,215 carries AEC-Q101 automotive qualification, making it suitable for automotive applications.

Q: What packaging considerations apply when substituting BC858ALT1 with Rohm parts?

A: BC858ALT1 uses SOT-23-3 package. Rohm 2SB1695 series use SMT3 or TSMT3 packages. While these packages are mechanically similar surface mount formats, PCB footprint dimensions differ. Verify that the substitute package footprint matches PCB design specifications before component procurement.

Q: Is BC858A-TP suitable for RoHS-regulated applications?

A: BC858A-TP does not specify RoHS compliance status in the provided data. For applications subject to RoHS regulations, select BC858ALT1G, 2SB1695 series, 2SB1706TL, 2SB1708TL, 2SB1710TL, BC857A,215, or BC858A RFG, all of which carry explicit RoHS3 compliance certification.

Q: What is the difference between BC858A RFG and BC858A-TP?

A: Both are BC858A variants with identical electrical specifications (100 mA Ic, 30 V Vce(br), 100 MHz fT, 125 hFE). BC858A RFG is manufactured by Taiwan Semiconductor Corporation with RoHS3 compliance and SOT-23 package. BC858A-TP is manufactured by Micro Commercial Co with SOT-23-3 package and unspecified RoHS status. Both are active products suitable for new designs.

Q: Can BC858AE6327HTSA1 be used in new designs?

A: BC858AE6327HTSA1 is classified as Last Time Buy, indicating that Infineon Technologies will discontinue this part. While electrically compatible with BC858ALT1 (100 mA Ic, 30 V Vce(br), 125 hFE) and offering enhanced transition frequency (250 MHz), its Last Time Buy status makes it unsuitable for new long-term designs. Select BC858ALT1G or other active alternatives for new product development.

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