BC550B A1G Equivalent & Substitute Parts

Part Overview

The BC550B A1G is an NPN bipolar junction transistor manufactured by Taiwan Semiconductor Corporation, designed for small-signal amplification applications. This device operates at a maximum collector voltage of 45 V with a collector current rating of 100 mA and power dissipation of 500 mW in a Through Hole TO-92 package. The BC550B A1G is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement continuity.

Key Parameters

Parameter	Value
Transistor Type	NPN
Current - Collector (Ic) (Max)	100 mA
Voltage - Collector Emitter Breakdown (Max)	45 V
Current - Collector Cutoff (Max)	15 nA (ICBO)
DC Current Gain (hFE) (Min) @ Ic, Vce	200 @ 2 mA, 5 V
Power - Max	500 mW
Operating Temperature	-65°C ~ 150°C (TJ)
Mounting Type	Through Hole
Package / Case	TO-92-3 (TO-226AA)

Substitute Part Grouping Explanation

Substitute parts for the BC550B A1G are selected based on strict electrical and mechanical parameter compatibility. The following criteria determine substitution eligibility:

Critical Matching Parameters:

Transistor Type: NPN
Maximum Collector Current: 100 mA
Maximum Collector-Emitter Breakdown Voltage: 45 V
Maximum Collector Cutoff Current: 15 nA (ICBO)
Package Type: TO-92-3 Through Hole
Mounting Type: Through Hole

Acceptable Parameter Variations:

DC Current Gain (hFE) may exceed the minimum specification of 200 @ 2 mA, 5 V
Power dissipation may equal or exceed 500 mW
Transition frequency may be specified (not required for BC550B A1G)
Operating temperature maximum may equal or exceed 150°C

All substitute parts listed maintain identical electrical ratings for collector current, collector-emitter breakdown voltage, and collector cutoff current. All substitute parts use the same TO-92-3 package configuration, ensuring mechanical and thermal compatibility.

Parameter Comparison

Part Number	Manufacturer	Product Status	Ic (Max)	Vce Breakdown (Max)	ICBO (Max)	hFE (Min) @ 2mA, 5V	Power (Max)	Frequency - Transition	Operating Temp (Max)	Package
BC550B A1G	Taiwan Semiconductor Corporation	Obsolete	100 mA	45 V	15 nA	200	500 mW	Not Specified	150°C	TO-92-3
BC547ATA	Fairchild Semiconductor	Active	100 mA	45 V	15 nA	110	500 mW	300 MHz	150°C	TO-92-3
BC547BTA	Fairchild Semiconductor	Active	100 mA	45 V	15 nA	200	625 mW	300 MHz	150°C	TO-92-3
BC547BTF	onsemi	Active	100 mA	45 V	15 nA	200	500 mW	300 MHz	150°C	TO-92-3
BC547CTA	onsemi	Active	100 mA	45 V	15 nA	420	500 mW	300 MHz	150°C	TO-92-3
BC547CTFR	onsemi	Active	100 mA	45 V	15 nA	420	500 mW	300 MHz	150°C	TO-92-3
BC550CTA	onsemi	Active	100 mA	45 V	15 nA	420	500 mW	300 MHz	150°C	TO-92-3

Engineering Selection Recommendations

All listed substitute parts meet the electrical and mechanical requirements for direct replacement of the BC550B A1G. Selection among available substitutes is based on product availability, compliance status, and packaging format.

Active Product Status: BC547ATA, BC547BTA, BC547BTF, BC547CTA, BC547CTFR, and BC550CTA are all classified as Active products, ensuring long-term availability and supply chain continuity compared to the obsolete BC550B A1G.

Compliance Certifications: All substitute parts are ROHS3 Compliant and REACH Unaffected, meeting current environmental and regulatory requirements. All parts carry EAR99 export classification.

DC Current Gain Considerations: BC547ATA exhibits a minimum hFE of 110 @ 2 mA, 5 V, which is lower than the BC550B A1G specification of 200. BC547BTA and BC547BTF maintain the 200 minimum hFE specification. BC547CTA, BC547CTFR, and BC550CTA provide higher minimum hFE of 420 @ 2 mA, 5 V. Higher hFE values do not prevent substitution but may affect circuit biasing in applications with tight gain requirements.

Power Dissipation: BC547BTA is rated for 625 mW maximum power dissipation, exceeding the 500 mW specification of the BC550B A1G. All other substitutes maintain the 500 mW rating.

Packaging Format: BC547ATA is supplied in Bulk packaging. BC547BTF, BC547CTA, BC547CTFR, and BC550CTA are supplied in Cut Tape (CT) format. Packaging format selection depends on assembly process requirements and procurement volume.

Frequently Asked Questions (FAQ)

Q: Can BC547 series transistors directly replace BC550B A1G in all applications?

A: Yes, BC547 series transistors (BC547ATA, BC547BTA, BC547BTF, BC547CTA, BC547CTFR) meet all critical electrical parameters for direct substitution. All devices share identical maximum collector current (100 mA), collector-emitter breakdown voltage (45 V), and collector cutoff current (15 nA) specifications. The TO-92-3 package ensures mechanical compatibility.

Q: What is the significance of different hFE values among substitute parts?

A: DC current gain (hFE) determines the amplification factor of the transistor. BC547ATA specifies a minimum hFE of 110, while BC547BTA and BC547BTF specify 200, and BC547CTA, BC547CTFR, and BC550CTA specify 420. Higher hFE values indicate greater current amplification. In circuits designed for the BC550B A1G with hFE of 200, substitutes with higher hFE will require circuit biasing adjustments to maintain equivalent operating points.

Q: Are there temperature operating range differences among substitutes?

A: BC547ATA, BC547BTA, BC547BTF, BC547CTA, BC547CTFR, and BC550CTA all specify a maximum operating temperature of 150°C, matching the BC550B A1G. BC547BTA additionally specifies a minimum operating temperature of -55°C, compared to the BC550B A1G minimum of -65°C. This difference is not significant for most applications operating within standard industrial temperature ranges.

Q: What is the difference between BC547 and BC550 base product numbers?

A: BC547 and BC550 are distinct base product numbers from different manufacturers. Both are NPN small-signal transistors with identical electrical ratings for this application. BC550CTA maintains the BC550 base product number while being manufactured by onsemi. Selection between BC547 and BC550 variants depends on design documentation requirements and supplier availability.

Q: Does the presence of transition frequency specification affect substitution?

A: Substitute parts BC547ATA, BC547BTA, BC547BTF, BC547CTA, BC547CTFR, and BC550CTA specify a transition frequency of 300 MHz, while the BC550B A1G does not specify this parameter. Specified transition frequency indicates higher-frequency capability and does not prevent substitution. Applications operating at frequencies below 300 MHz are unaffected by this specification difference.

Q: What packaging format should be selected for procurement?

A: BC547ATA is supplied in Bulk packaging. BC547BTF, BC547CTA, BC547CTFR, and BC550CTA are supplied in Cut Tape (CT) format. Bulk packaging is suitable for high-volume applications and manual assembly. Cut Tape format is optimized for automated pick-and-place assembly processes. Selection depends on manufacturing process requirements and order volume.

Q: Are all substitute parts RoHS3 Compliant?

A: Yes, BC547BTF, BC547CTA, BC547CTFR, and BC550CTA are explicitly marked as ROHS3 Compliant. All substitute parts are REACH Unaffected and carry EAR99 export classification, meeting current environmental and regulatory requirements.

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