BC548BU Equivalent & Substitute Parts

Part Overview

The BC548BU is an NPN bipolar junction transistor manufactured by onsemi, designed for small-signal amplification and switching applications. This device operates at a maximum collector voltage of 30 V with a collector current rating of 100 mA and delivers 500 mW maximum power dissipation. The BC548BU features a transition frequency of 300 MHz and is housed in a TO-92-3 through-hole package.

The BC548BU is classified as obsolete, which necessitates identification of equivalent and substitute components for new designs and ongoing production requirements. Equivalent parts maintain identical electrical and mechanical specifications, while substitute parts provide functional alternatives with modified parameters suitable for specific application requirements.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Collector Current (Max)	100	mA
Collector-Emitter Breakdown Voltage (Max)	30	V
Vce Saturation (Max)	600	mV @ 5mA, 100mA
Collector Cutoff Current (Max)	15	nA
DC Current Gain (hFE Min)	110	@ 2mA, 5V
Power Dissipation (Max)	500	mW
Transition Frequency	300	MHz
Operating Temperature (Max)	150	°C
Mounting Type	Through Hole	—
Package	TO-92-3	—

Substitute Part Grouping Explanation

Substitution of the BC548BU is determined by strict adherence to the following electrical and mechanical parameters:

Mandatory Compatibility Criteria:

Transistor Type: NPN configuration required
Collector Current (Max): 100 mA minimum
Collector-Emitter Breakdown Voltage: 30 V minimum
Vce Saturation: 600 mV maximum @ 5mA, 100mA
Collector Cutoff Current: 15 nA maximum
DC Current Gain (hFE): 110 minimum @ 2mA, 5V
Power Dissipation: 500 mW minimum
Transition Frequency: 300 MHz minimum
Operating Temperature: 150°C maximum
Mounting Type: Through Hole
Package: TO-92-3 compatible

Parametric Equivalent: The BC548BU from Fairchild Semiconductor maintains identical electrical specifications and package configuration, providing direct substitution without circuit modification.

Functional Substitute: The BC546BTA from onsemi provides enhanced voltage rating (65 V vs. 30 V) and improved DC current gain (200 vs. 110), making it suitable for applications requiring higher voltage headroom while maintaining all other critical parameters.

Parameter Comparison

Parameter	BC548BU (onsemi)	BC548BU (Fairchild)	BC546BTA (onsemi)
Transistor Type	NPN	NPN	NPN
Collector Current (Max)	100 mA	100 mA	100 mA
Collector-Emitter Breakdown Voltage (Max)	30 V	30 V	65 V
Vce Saturation (Max)	600 mV	600 mV	600 mV
Collector Cutoff Current (Max)	15 nA	15 nA	15 nA
DC Current Gain (hFE Min)	110 @ 2mA, 5V	110 @ 2mA, 5V	200 @ 2mA, 5V
Power Dissipation (Max)	500 mW	500 mW	500 mW
Transition Frequency	300 MHz	300 MHz	300 MHz
Operating Temperature (Max)	150°C	150°C	150°C
Mounting Type	Through Hole	Through Hole	Through Hole
Package	TO-92-3	TO-92-3	TO-92-3
Product Status	Obsolete	Active	Active
RoHS Status	ROHS3 Compliant	Not Specified	ROHS3 Compliant

Engineering Selection Recommendations

BC548BU (Fairchild Semiconductor): This parametric equivalent provides identical electrical performance and package configuration to the onsemi BC548BU. Selection of the Fairchild variant is appropriate for applications where the original onsemi component is unavailable. Both devices maintain ROHS3 compliance status and are classified as active products, ensuring continued availability and supply chain stability.

BC546BTA (onsemi): This substitute component is suitable for applications where the circuit design permits operation at elevated collector-emitter voltages. The BC546BTA offers a 65 V breakdown voltage rating compared to the 30 V specification of the BC548BU, providing enhanced voltage margin in circuits operating near the maximum rating of the original device. The increased DC current gain (200 vs. 110) results in improved base drive efficiency. The BC546BTA maintains ROHS3 compliance and active product status, ensuring long-term availability. This component is packaged in Cut Tape format with formed leads, maintaining TO-92-3 package compatibility.

Selection between the parametric equivalent and functional substitute depends on circuit voltage requirements and base drive considerations. Both alternatives are active products with established supply chains.

Frequently Asked Questions (FAQ)

Q: Can the BC548BU (Fairchild) be used as a direct replacement for the BC548BU (onsemi)?

A: Yes. The Fairchild BC548BU maintains identical electrical specifications including collector current, breakdown voltage, saturation voltage, current gain, power dissipation, and transition frequency. Both devices use the TO-92-3 package with through-hole mounting. Direct substitution is supported without circuit modification.

Q: Under what conditions is the BC546BTA suitable as a substitute for the BC548BU?

A: The BC546BTA is suitable when the circuit design permits operation at the higher collector-emitter breakdown voltage of 65 V. Applications operating the BC548BU near its 30 V maximum rating benefit from the additional voltage margin provided by the BC546BTA. The higher DC current gain of the BC546BTA (200 vs. 110) reduces base drive requirements. All other critical parameters including collector current, saturation voltage, power dissipation, and transition frequency remain compatible.

Q: Are there package compatibility concerns when substituting these parts?

A: All three components use the TO-92-3 through-hole package. The BC546BTA features formed leads, while the BC548BU variants use standard leads. Both configurations are compatible with standard TO-92-3 footprints and through-hole PCB layouts. No package-related modifications are required.

Q: What is the significance of the obsolete status of the BC548BU (onsemi)?

A: The obsolete classification indicates that onsemi has discontinued production of this component. The BC548BU (Fairchild) and BC546BTA (onsemi) are both active products with established supply chains, making them appropriate selections for new designs and ongoing production requirements.

Q: Do all substitute options maintain RoHS compliance?

A: The BC548BU (onsemi) and BC546BTA (onsemi) are both ROHS3 compliant. RoHS status for the Fairchild BC548BU is not specified in the provided documentation. Compliance verification with the Fairchild component is required for applications with mandatory RoHS requirements.

Q: How do the DC current gain specifications affect circuit design?

A: The BC548BU specifies a minimum DC current gain (hFE) of 110 at 2 mA collector current and 5 V collector-emitter voltage. The BC546BTA specifies a minimum hFE of 200 under identical conditions. Higher current gain reduces the base current required to achieve a given collector current, resulting in lower power dissipation in the base circuit. Circuit designs relying on specific current gain values must account for the minimum specified gain to ensure proper operation across the component tolerance range.

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