BC549 Equivalent & Substitute Parts

Part Overview

The BC549 is a small-signal NPN bipolar junction transistor manufactured by onsemi, designed for general-purpose switching and amplification applications. The device operates at a maximum collector voltage of 30 V with a collector current rating of 100 mA and a maximum power dissipation of 500 mW. The BC549 is classified as obsolete, which necessitates identification of active equivalent components for continued circuit implementation and procurement.

Key Parameters

Parameter	Value
Transistor Type	NPN
Current - Collector (Ic) (Max)	100 mA
Voltage - Collector Emitter Breakdown (Max)	30 V
Vce Saturation (Max) @ Ib, Ic	600 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	300 MHz
Operating Temperature (TJ)	150°C
Mounting Type	Through Hole
Package / Case	TO-92-3 (TO-226AA)

Substitute Part Grouping Explanation

Substitution of the BC549 is determined by electrical and mechanical parameter equivalence across the following criteria:

Electrical Parameters:

Transistor polarity: NPN configuration
Maximum collector current: 100 mA
Maximum collector-emitter breakdown voltage: 30 V
Saturation voltage characteristics: 600 mV @ 5 mA, 100 mA
Collector cutoff current: 15 nA (ICBO)
DC current gain (hFE): minimum 110 @ 2 mA, 5 V
Maximum power dissipation: 500 mW
Transition frequency: 300 MHz
Maximum junction temperature: 150°C

Mechanical Parameters:

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

The BC548BU meets all specified electrical and mechanical parameters and is classified as an active product, making it a direct parametric equivalent for the obsolete BC549.

Parameter Comparison

Parameter	BC549 (onsemi)	BC548BU (Fairchild Semiconductor)	Match
Transistor Type	NPN	NPN	Yes
Current - Collector (Ic) (Max)	100 mA	100 mA	Yes
Voltage - Collector Emitter Breakdown (Max)	30 V	30 V	Yes
Vce Saturation (Max) @ Ib, Ic	600 mV @ 5 mA, 100 mA	600 mV @ 5 mA, 100 mA	Yes
Current - Collector Cutoff (Max)	15 nA (ICBO)	15 nA (ICBO)	Yes
DC Current Gain (hFE) (Min) @ Ic, Vce	110 @ 2 mA, 5 V	110 @ 2 mA, 5 V	Yes
Power - Max	500 mW	500 mW	Yes
Frequency - Transition	300 MHz	300 MHz	Yes
Operating Temperature (TJ)	150°C	150°C	Yes
Mounting Type	Through Hole	Through Hole	Yes
Package / Case	TO-92-3 (TO-226AA)	TO-92-3 (TO-226AA)	Yes
Product Status	Obsolete	Active	Active preferred

Engineering Selection Recommendations

The BC548BU manufactured by Fairchild Semiconductor is a direct parametric equivalent to the BC549. All electrical specifications, including collector current, breakdown voltage, saturation characteristics, current gain, power rating, and transition frequency, are identical. The mechanical package designation and through-hole mounting configuration are also equivalent.

The primary advantage of selecting the BC548BU is its active product status. The BC549 is classified as obsolete, which presents long-term procurement and supply chain risks. The BC548BU maintains full compatibility with existing circuit designs while ensuring continued availability and manufacturing support.

Both devices carry identical ECCN (EAR99) and HTSUS (8541.21.0075) classifications, confirming regulatory equivalence for export and tariff purposes.

Frequently Asked Questions (FAQ)

Q: Can the BC548BU be used as a direct replacement for the BC549 in existing circuit designs?

A: Yes. The BC548BU is a parametric equivalent with identical electrical and mechanical specifications. No circuit modifications are required for substitution.

Q: Are there any differences in pin configuration between the BC549 and BC548BU?

A: No. Both devices use the TO-92-3 (TO-226AA) package with identical pin assignments. Pin-for-pin substitution is supported.

Q: Why is the BC549 classified as obsolete?

A: The BC549 has been discontinued by onsemi. The BC548BU provides equivalent functionality with active manufacturing support.

Q: What is the significance of the product status difference?

A: Active products have ongoing manufacturing, quality assurance, and supply chain support. Obsolete products have limited or no availability and no manufacturing guarantees. For new designs or long-term applications, active equivalents are preferred.

Q: Are the electrical performance characteristics identical between the two devices?

A: Yes. Maximum collector current (100 mA), breakdown voltage (30 V), saturation voltage (600 mV @ 5 mA, 100 mA), current gain (110 @ 2 mA, 5 V), power dissipation (500 mW), and transition frequency (300 MHz) are identical.

Q: Can the BC548BU handle the same operating temperature range as the BC549?

A: Yes. Both devices are rated for a maximum junction temperature of 150°C.

Q: Is the through-hole mounting configuration the same for both devices?

A: Yes. Both the BC549 and BC548BU use through-hole mounting in the TO-92-3 package, allowing direct PCB substitution without layout modifications.

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