BC556CTA Equivalent & Substitute Parts

Part Overview

The BC556CTA is a small-signal PNP bipolar junction transistor manufactured by onsemi, designed for general-purpose switching and amplification applications. It features a maximum collector current of 100 mA, collector-emitter breakdown voltage of 65 V, and a transition frequency of 150 MHz. The device is packaged in a TO-92-3 through-hole configuration with a maximum power dissipation of 500 mW.

The BC556CTA is classified as obsolete. Locating equivalent substitute parts is necessary to maintain design continuity and ensure component availability for new production runs, repairs, and system upgrades where this transistor is specified.

Key Parameters

Parameter	Value	Unit
Transistor Type	PNP	—
Current - Collector (Ic) (Max)	100	mA
Voltage - Collector Emitter Breakdown (Max)	65	V
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	420	@ 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)	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the BC556CTA is determined by strict equivalence across the following electrical and mechanical parameters:

Critical Matching Parameters:

Transistor polarity: PNP
Maximum collector current: 100 mA
Collector-emitter breakdown voltage: 65 V
Vce saturation voltage: 650 mV @ 5 mA, 100 mA
Collector cutoff current: 15 nA (ICBO)
Maximum power dissipation: 500 mW
Transition frequency: 150 MHz
Operating temperature range: 150°C (TJ)
Package type: TO-92-3 through-hole configuration

The BC556BTA meets all critical electrical specifications and physical packaging requirements, establishing it as a direct functional equivalent. Variations in DC current gain (hFE) minimum values do not disqualify substitution when the specified gain remains within acceptable circuit design margins.

Parameter Comparison

Parameter	BC556CTA (onsemi)	BC556BTA (Fairchild Semiconductor)	Match Status
Transistor Type	PNP	PNP	Equivalent
Current - Collector (Ic) (Max)	100 mA	100 mA	Equivalent
Voltage - Collector Emitter Breakdown (Max)	65 V	65 V	Equivalent
Vce Saturation (Max) @ Ib, Ic	650 mV @ 5 mA, 100 mA	650 mV @ 5 mA, 100 mA	Equivalent
Current - Collector Cutoff (Max)	15 nA (ICBO)	15 nA (ICBO)	Equivalent
DC Current Gain (hFE) (Min) @ Ic, Vce	420 @ 2 mA, 5 V	200 @ 2 mA, 5 V	BC556BTA lower; within substitution tolerance
Power - Max	500 mW	500 mW	Equivalent
Frequency - Transition	150 MHz	150 MHz	Equivalent
Operating Temperature (TJ)	150°C	150°C	Equivalent
Mounting Type	Through Hole	Through Hole	Equivalent
Package / Case	TO-92-3 (TO-226AA)	TO-92-3 (TO-226AA)	Equivalent

Engineering Selection Recommendations

BC556BTA (Fairchild Semiconductor) is the qualified substitute for the obsolete BC556CTA.

Selection Basis:

The BC556BTA is classified as an active product with current manufacturing status and established supply chain availability (18,244 units in stock). All critical electrical parameters match the BC556CTA specification, including collector current, breakdown voltage, saturation voltage, cutoff current, power dissipation, and transition frequency. The physical package (TO-92-3 through-hole) is identical, ensuring direct mechanical compatibility in existing PCB layouts.

The DC current gain (hFE) minimum of 200 @ 2 mA, 5 V on the BC556BTA is lower than the BC556CTA specification of 420 @ 2 mA, 5 V. This difference does not prevent substitution in applications where circuit design accommodates the lower gain specification. Design verification is required only if the original circuit depends on the higher gain value for critical bias or amplification performance.

Both parts carry identical export control classifications (ECCN: EAR99) and tariff codes (HTSUS: 8541.21.0075), supporting regulatory compliance continuity.

Frequently Asked Questions (FAQ)

Q: Can the BC556BTA directly replace the BC556CTA in existing designs?

A: Yes. The BC556BTA meets all critical electrical specifications and uses the identical TO-92-3 through-hole package. Direct pin-for-pin substitution is supported. Circuit performance depends on whether the design margin accommodates the lower DC current gain specification of the BC556BTA.

Q: What is the significance of the DC current gain (hFE) difference between these parts?

A: The BC556CTA specifies a minimum hFE of 420 @ 2 mA, 5 V, while the BC556BTA specifies 200 @ 2 mA, 5 V. In amplifier circuits, this difference affects voltage gain and biasing conditions. In switching applications with sufficient base drive, the lower gain does not impact functionality. Circuit analysis is required to confirm compatibility in gain-sensitive designs.

Q: Are the package dimensions and lead configurations identical?

A: Yes. Both the BC556CTA and BC556BTA use the TO-92-3 (TO-226AA) package with formed leads. PCB footprints, lead spacing, and mounting hole requirements are identical. No layout modifications are necessary.

Q: What is the product status difference, and why does it matter?

A: The BC556CTA is obsolete; the BC556BTA is active. Active status indicates current manufacturing, established supply chains, and long-term availability. The BC556BTA is the recommended choice for new designs and production continuity.

Q: Are there any compliance or regulatory differences between these parts?

A: No. Both parts carry identical export control classifications (ECCN: EAR99) and tariff codes (HTSUS: 8541.21.0075). Regulatory compliance is maintained with substitution.

Q: What is the moisture sensitivity level, and does it affect handling?

A: Both parts are classified as MSL 1 (Unlimited), indicating no moisture sensitivity. Standard handling procedures apply; no special dry-pack storage or baking procedures are required.

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