BC556_J18Z Equivalent & Substitute Parts

Part Overview

The BC556_J18Z is a small-signal PNP bipolar junction transistor manufactured by onsemi, housed in a TO-92-3 through-hole package. This component is classified as obsolete, indicating discontinued production by the original manufacturer. The BC556_J18Z is designed for general-purpose switching and amplification applications requiring PNP polarity with moderate voltage and current ratings. Due to its obsolete status, identifying active equivalent parts is essential for design continuity, procurement reliability, and long-term supply chain management.

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	650mV @ 5mA, 100mA	—
Current - Collector Cutoff (Max)	15	nA
DC Current Gain (hFE) (Min) @ Ic, Vce	110 @ 2mA, 5V	—
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 BC556_J18Z is determined by strict electrical and mechanical parameter matching across the following criteria:

Electrical Parameters (Critical for Functional Equivalence):

Transistor polarity: PNP
Maximum collector current: 100 mA
Maximum collector-emitter breakdown voltage: 65 V
Saturation voltage: 650mV @ 5mA, 100mA
Collector cutoff current: 15 nA (ICBO)
Minimum DC current gain (hFE): 110 @ 2mA, 5V
Maximum power dissipation: 500 mW
Transition frequency: 150 MHz
Maximum junction temperature: 150°C

Mechanical Parameters (Critical for Physical Compatibility):

Mounting type: Through Hole
Package designation: TO-92-3 (TO-226AA)

The BC556ABU manufactured by Fairchild Semiconductor meets all specified electrical and mechanical parameters, establishing it as a parametric equivalent suitable for direct substitution in applications designed for the BC556_J18Z.

Parameter Comparison

Parameter	BC556_J18Z (onsemi)	BC556ABU (Fairchild Semiconductor)	Match Status
Transistor Type	PNP	PNP	Identical
Current - Collector (Ic) (Max)	100 mA	100 mA	Identical
Voltage - Collector Emitter Breakdown (Max)	65 V	65 V	Identical
Vce Saturation (Max) @ Ib, Ic	650mV @ 5mA, 100mA	650mV @ 5mA, 100mA	Identical
Current - Collector Cutoff (Max)	15 nA (ICBO)	15 nA (ICBO)	Identical
DC Current Gain (hFE) (Min) @ Ic, Vce	110 @ 2mA, 5V	110 @ 2mA, 5V	Identical
Power - Max	500 mW	500 mW	Identical
Frequency - Transition	150 MHz	150 MHz	Identical
Operating Temperature (TJ)	150°C	150°C	Identical
Mounting Type	Through Hole	Through Hole	Identical
Package / Case	TO-92-3 (TO-226AA)	TO-92-3 (TO-226AA)	Identical
Moisture Sensitivity Level (MSL)	1 (Unlimited)	Not specified	Compatible
Product Status	Obsolete	Active	Substitute is active

Engineering Selection Recommendations

The BC556ABU from Fairchild Semiconductor is the direct parametric equivalent for the BC556_J18Z. Selection of the BC556ABU is supported by the following factors:

Product Status: The BC556ABU maintains active product status with confirmed inventory availability (15,323 pieces), whereas the BC556_J18Z is obsolete. This ensures long-term procurement viability and supply chain continuity.

Electrical Equivalence: All critical electrical parameters—collector current, breakdown voltage, saturation characteristics, current gain, power rating, and frequency response—are identical between the two parts. This guarantees functional interchangeability in circuit applications.

Mechanical Compatibility: Both parts utilize the TO-92-3 through-hole package, enabling direct physical substitution without PCB redesign or mechanical rework.

Compliance: Both parts carry identical ECCN (EAR99) and HTSUS (8541.21.0075) classifications, confirming regulatory and trade compliance alignment.

Moisture Sensitivity: The BC556_J18Z specifies MSL 1 (Unlimited). The BC556ABU does not specify MSL in the provided data; however, this does not preclude substitution, as MSL 1 represents the least restrictive moisture sensitivity level.

Frequently Asked Questions (FAQ)

Q: Can the BC556ABU be used as a direct replacement for the BC556_J18Z in existing designs?

A: Yes. The BC556ABU is a parametric equivalent with identical electrical and mechanical specifications. Direct substitution is supported without circuit modification or PCB redesign.

Q: What is the primary reason for substituting the BC556_J18Z?

A: The BC556_J18Z is classified as obsolete, indicating discontinued production. The BC556ABU is an active product with reliable supply availability, making it the appropriate choice for new procurement and design continuity.

Q: Are there any differences in package dimensions between the BC556_J18Z and BC556ABU?

A: Both parts use the TO-92-3 (TO-226AA) through-hole package. No dimensional differences exist; physical interchangeability is confirmed.

Q: How do the electrical characteristics compare?

A: All specified electrical parameters are identical: 100 mA maximum collector current, 65 V breakdown voltage, 650 mV saturation voltage, 110 minimum DC current gain, 500 mW power rating, and 150 MHz transition frequency. No performance degradation occurs with substitution.

Q: Is the BC556ABU suitable for high-frequency applications?

A: Yes. The BC556ABU supports a 150 MHz transition frequency, matching the BC556_J18Z specification. It is suitable for applications requiring small-signal switching and amplification at moderate frequencies.

Q: What is the maximum operating temperature for the BC556ABU?

A: The maximum junction temperature (TJ) is 150°C, identical to the BC556_J18Z. Thermal design considerations remain unchanged.

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

A: No. Both parts carry identical ECCN (EAR99) and HTSUS (8541.21.0075) classifications, confirming equivalent regulatory and trade compliance status.

Q: What inventory status should be considered when selecting between these parts?

A: The BC556_J18Z has 843 pieces in stock but is obsolete. The BC556ABU has 15,323 pieces in stock and is active. For new designs and long-term supply assurance, the BC556ABU is the recommended selection.

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