BC550 NPN Bipolar Transistor Equivalent & Substitute Parts

Part Overview

The BC550 is an NPN bipolar junction transistor manufactured by onsemi, housed in a TO-92-3 through-hole package. This device is rated for 45 V collector-emitter breakdown voltage with a maximum collector current of 100 mA and 500 mW power dissipation. The BC550 operates at a transition frequency of 300 MHz and is suitable for general-purpose amplification and switching applications in through-hole circuit designs.

The BC550 is classified as an obsolete product. Equivalent and substitute parts are necessary to support ongoing maintenance, repair, and redesign of legacy systems, as well as to provide alternative packaging and performance options for new designs requiring similar electrical characteristics.

Substiute Parts

BC550

onsemiIn Stock: 2153BC550 Datasheet

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MMBT100

onsemiIn Stock: 65415MMBT100 Datasheet

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2N5232A PBFREE

Central Semiconductor CorpIn Stock: 178042N5232A PBFREE Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the BC550 are identified based on electrical compatibility within the following criteria:

Primary Compatibility Parameters:

• Transistor type: NPN
• Voltage rating: Collector-emitter breakdown voltage ≥ 45 V
• Current rating: Maximum collector current ≥ 100 mA
• Power dissipation: Maximum power ≥ 500 mW

Secondary Compatibility Parameters:

• DC current gain (hFE) characteristics suitable for amplification and switching
• Transition frequency adequate for intended frequency range
• Saturation voltage characteristics compatible with switching applications

Substitute parts are grouped into two categories:

Category 1: Through-Hole Equivalents — Parts maintaining the same through-hole mounting technology and package form factor, enabling direct mechanical and electrical substitution in existing PCB designs.

Category 2: Surface-Mount Alternatives — Parts offering equivalent electrical performance in surface-mount packaging, suitable for redesigned circuits or new applications requiring compact form factors.

Parameter Comparison

Engineering Selection Recommendations

For Through-Hole Circuit Designs:

The 2N5232A PBFREE is the primary substitute for direct replacement in through-hole applications. This part maintains the TO-92-3 package form factor, enabling mechanical compatibility with existing PCB layouts. The 2N5232A PBFREE exceeds the BC550 in voltage rating (50 V vs. 45 V), maximum collector current (100 mA), and power dissipation (625 mW vs. 500 mW). The device exhibits superior DC current gain (250 @ 2mA, 5V vs. 110 @ 2mA, 5V) and significantly lower saturation voltage (125 mV vs. 600 mV), resulting in improved switching performance and reduced power loss. The 2N5232A PBFREE is ROHS3 compliant and carries active product status, ensuring long-term availability and supply chain stability.

For Surface-Mount Circuit Designs:

The MMBT100 provides equivalent electrical performance in a compact surface-mount SOT-23-3 package. This part is manufactured by onsemi and maintains the same 45 V voltage rating as the BC550. The MMBT100 supports higher maximum collector current (500 mA vs. 100 mA), enabling use in higher-current applications. The device operates at 250 MHz transition frequency, slightly lower than the BC550 (300 MHz), but adequate for most general-purpose amplification and switching circuits. The MMBT100 is ROHS3 compliant and carries active product status. Selection of the MMBT100 requires PCB redesign to accommodate surface-mount technology.

Compliance and Availability:

Both substitute parts are ROHS3 compliant and carry active product status, ensuring regulatory compliance and sustained component availability. The BC550, classified as obsolete, presents long-term supply risk. Migration to either substitute part is recommended for new designs and for maintenance applications where component availability is critical.

Frequently Asked Questions (FAQ)

Q: Can the MMBT100 be used as a direct replacement for the BC550 in existing through-hole PCB designs?

A: No. The MMBT100 uses surface-mount SOT-23-3 packaging, while the BC550 uses through-hole TO-92-3 packaging. Direct PCB substitution is not possible without circuit board redesign. However, the MMBT100 can be adapted using surface-mount to through-hole adapter boards or by manual wiring if circuit layout permits.

Q: Is the 2N5232A PBFREE a pin-compatible replacement for the BC550?

A: Yes. Both the BC550 and 2N5232A PBFREE use the TO-92-3 through-hole package with identical pin configurations (Base, Collector, Emitter). The 2N5232A PBFREE can be substituted directly into existing PCB designs without modification.

Q: What are the key electrical differences between the BC550 and 2N5232A PBFREE?

A: The 2N5232A PBFREE exceeds the BC550 in voltage rating (50 V vs. 45 V), power dissipation (625 mW vs. 500 mW), and DC current gain (250 vs. 110 @ 2mA, 5V). The 2N5232A PBFREE exhibits lower saturation voltage (125 mV vs. 600 mV), resulting in reduced power loss during switching. These differences make the 2N5232A PBFREE suitable for applications requiring higher performance margins and improved efficiency.

Q: Why is the MMBT100 rated for higher collector current (500 mA) than the BC550 (100 mA)?

A: The MMBT100 is a higher-performance variant designed for applications requiring greater current handling capacity. The increased current rating reflects the device's enhanced thermal and electrical design. Applications requiring only 100 mA operation can safely use the MMBT100 without derating concerns.

Q: Are there any frequency limitations when substituting the MMBT100 for the BC550?

A: The MMBT100 operates at 250 MHz transition frequency, compared to the BC550 at 300 MHz. For applications operating below 250 MHz, the MMBT100 is fully compatible. Applications requiring operation above 250 MHz should verify that the reduced transition frequency does not impact circuit performance.

Q: What is the significance of the lower saturation voltage in the 2N5232A PBFREE?

A: Lower saturation voltage (125 mV vs. 600 mV) indicates reduced voltage drop across the transistor during saturation. This characteristic reduces power dissipation in switching applications and improves circuit efficiency. In switching circuits, the 2N5232A PBFREE generates less heat and allows lower supply voltages for equivalent performance.

Q: Are both substitute parts RoHS compliant?

A: Yes. Both the MMBT100 and 2N5232A PBFREE are ROHS3 compliant. The BC550 does not specify RoHS status. For applications subject to RoHS regulations, either substitute part is acceptable.

Q: What is the product status significance for component selection?

A: The BC550 is classified as obsolete, indicating discontinued production and limited future availability. Both substitute parts carry active product status, ensuring sustained manufacturing and supply chain support. For new designs and long-term maintenance applications, active-status parts are preferred to avoid future supply disruptions.