BC556BU Equivalent & Substitute Parts

Part Overview

The BC556BU is a small-signal PNP bipolar junction transistor manufactured by onsemi, housed in a TO-92-3 through-hole package. This device is rated for 65 V collector-emitter breakdown voltage, 100 mA maximum collector current, and 500 mW power dissipation. The BC556BU operates at a transition frequency of 150 MHz with a maximum junction temperature of 150°C.

The BC556BU is classified as obsolete. Equivalent and substitute parts are necessary to maintain design continuity and ensure component availability for new production runs, repairs, and system upgrades where the original part is no longer readily available from the original manufacturer.

Key Parameters

Parameter	Value	Unit
Transistor Type	PNP	—
Voltage - Collector Emitter Breakdown (Max)	65	V
Current - Collector (Ic) (Max)	100	mA
Vce Saturation (Max) @ Ib, Ic	650 mV @ 5 mA, 100 mA	—
Current - Collector Cutoff (Max)	15	nA (ICBO)
DC Current Gain (hFE) (Min) @ Ic, Vce	110 @ 2 mA, 5 V	—
Power - Max	500	mW
Frequency - Transition	150	MHz
Operating Temperature (TJ)	150	°C
Mounting Type	Through Hole	—
Package / Case	TO-92-3 (TO-226AA)	—

Substitute Part Grouping Explanation

Substitution of the BC556BU is determined by strict equivalence across the following critical parameters:

Transistor Type: PNP polarity must be maintained
Voltage - Collector Emitter Breakdown (Max): 65 V minimum
Current - Collector (Ic) (Max): 100 mA minimum
Vce Saturation (Max): 650 mV @ 5 mA, 100 mA
Current - Collector Cutoff (Max): 15 nA (ICBO) maximum
Power - Max: 500 mW minimum
Frequency - Transition: 150 MHz minimum
Operating Temperature (TJ): 150°C minimum
Package / Case: TO-92-3 (TO-226AA) through-hole configuration

Substitute parts must meet or exceed all specified electrical parameters and maintain identical package geometry and pin configuration to ensure direct board-level compatibility without circuit modification.

Parameter Comparison

Parameter	BC556BU (onsemi)	BC556ABU (Fairchild)	BC556BTA (Fairchild)
Transistor Type	PNP	PNP	PNP
Voltage - Collector Emitter Breakdown (Max)	65 V	65 V	65 V
Current - Collector (Ic) (Max)	100 mA	100 mA	100 mA
Vce Saturation (Max) @ Ib, Ic	650 mV @ 5 mA, 100 mA	650 mV @ 5 mA, 100 mA	650 mV @ 5 mA, 100 mA
Current - Collector Cutoff (Max)	15 nA (ICBO)	15 nA (ICBO)	15 nA (ICBO)
DC Current Gain (hFE) (Min) @ Ic, Vce	110 @ 2 mA, 5 V	110 @ 2 mA, 5 V	200 @ 2 mA, 5 V
Power - Max	500 mW	500 mW	500 mW
Frequency - Transition	150 MHz	150 MHz	150 MHz
Operating Temperature (TJ)	150°C	150°C	150°C
Mounting Type	Through Hole	Through Hole	Through Hole
Package / Case	TO-92-3 (TO-226AA)	TO-92-3 (TO-226AA)	TO-92-3 (TO-226AA)
Product Status	Obsolete	Active	Active

Engineering Selection Recommendations

BC556ABU (Fairchild Semiconductor) is a parametric equivalent substitute for the BC556BU. This part maintains identical electrical specifications including DC current gain (hFE) of 110 @ 2 mA, 5 V, and is currently in active production status. The BC556ABU is available in high inventory quantities and carries the same ECCN and HTSUS classifications as the original part.

BC556BTA (Fairchild Semiconductor) is a functional substitute for the BC556BU with one notable difference: the DC current gain (hFE) is specified at 200 @ 2 mA, 5 V, which exceeds the minimum requirement of 110. All other electrical parameters, package configuration, and compliance certifications are identical. The BC556BTA is in active production with substantial inventory availability.

Both substitute parts are manufactured by Fairchild Semiconductor, carry active product status, and are suitable for direct replacement in applications where the BC556BU was originally specified. Selection between BC556ABU and BC556BTA depends on circuit requirements regarding current gain tolerance and performance margins.

Frequently Asked Questions (FAQ)

Q: Can the BC556ABU be used as a direct replacement for the BC556BU?

A: Yes. The BC556ABU meets all electrical specifications of the BC556BU, including voltage rating (65 V), current rating (100 mA), power dissipation (500 mW), transition frequency (150 MHz), and DC current gain (110 @ 2 mA, 5 V). The TO-92-3 package and through-hole mounting configuration are identical, enabling direct board-level substitution without circuit modification.

Q: What is the difference between BC556ABU and BC556BTA?

A: Both parts are functionally equivalent to the BC556BU across all critical parameters. The primary difference is DC current gain: BC556ABU specifies 110 @ 2 mA, 5 V (matching the original), while BC556BTA specifies 200 @ 2 mA, 5 V. The higher gain of BC556BTA provides additional performance margin in current-gain-dependent circuits but does not affect voltage, current, or frequency specifications.

Q: Are there any package or pinout differences between these substitutes?

A: No. All three parts—BC556BU, BC556ABU, and BC556BTA—use the TO-92-3 (TO-226AA) through-hole package with identical pinout and lead configuration. No PCB layout modifications are required for substitution.

Q: Why is the BC556BU listed as obsolete?

A: The BC556BU is classified as obsolete by onsemi, indicating that the manufacturer has discontinued production. Equivalent and substitute parts from active manufacturers such as Fairchild Semiconductor ensure continued design support and component availability.

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

A: For new designs, either BC556ABU or BC556BTA is acceptable. BC556ABU maintains exact parametric equivalence to the original BC556BU. BC556BTA offers higher DC current gain (200 vs. 110), which may provide improved performance in applications sensitive to current gain variation. Selection should be based on circuit design requirements and performance margins.

Q: Are the substitute parts RoHS and REACH compliant?

A: Both BC556ABU and BC556BTA carry ECCN EAR99 and HTSUS 8541.21.0075 classifications, consistent with the original BC556BU. Compliance documentation should be verified with the specific supplier for RoHS and REACH status applicable to your procurement requirements.

Request Quote (Ships tomorrow)

Part Number

Quantity

Company

Contact Name

E-mail

Message