2SA733-Q-AP Equivalent & Substitute Parts

Part Overview

The 2SA733-Q-AP is a PNP bipolar junction transistor manufactured by Micro Commercial Co, designed for small-signal switching and amplification applications. Specified for 50 V collector-emitter breakdown voltage with 100 mA maximum collector current, this component is housed in a TO-92 through-hole package. The 2SA733-Q-AP is classified as obsolete, necessitating identification of active equivalent parts for new designs and ongoing production requirements. Substitute parts must maintain functional compatibility across critical electrical parameters including voltage rating, current capacity, and thermal characteristics.

Substiute Parts

2SA733-Q-AP

Micro Commercial CoIn Stock: 9412SA733-Q-AP Datasheet

Current PartRFQ

BC557ATA

Fairchild SemiconductorIn Stock: 860BC557ATA Datasheet

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BC557BTA

onsemiIn Stock: 6210BC557BTA Datasheet

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BC557BTF

onsemiIn Stock: 41658BC557BTF Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the 2SA733-Q-AP are qualified based on the following substitution criteria:

Mandatory Compatibility Parameters:

• Transistor Type: PNP configuration
• Current - Collector (Ic) (Max): 100 mA minimum
• Mounting Type: Through Hole
• Package / Case: TO-92-3 compatible

Acceptable Parameter Variations:

• Voltage - Collector Emitter Breakdown (Max): Substitute parts rated at 45 V are acceptable for applications where the 2SA733-Q-AP operates at or below 45 V. The 50 V rating of the original part provides additional voltage margin; however, 45 V rated substitutes remain functional in circuits designed within this lower threshold.
• Power - Max: Substitute parts rated at 500 mW exceed the 250 mW specification of the original part, providing enhanced thermal headroom.
• Frequency - Transition: Substitute parts rated at 150MHz exceed the 100MHz specification, maintaining or improving high-frequency performance.
• DC Current Gain (hFE): Substitute parts with higher minimum hFE values (110–200 @ 2mA, 5V) provide improved current amplification characteristics compared to the original 135 @ 1mA, 6V specification.
• Product Status: Active substitute parts ensure ongoing availability and supply chain continuity.

Parameter Comparison

Engineering Selection Recommendations

BC557BTF (onsemi) is the primary substitute for the 2SA733-Q-AP. This part is active in production, ROHS3 compliant, and available in high inventory (41,626 pcs). The BC557BTF maintains PNP configuration, 100 mA collector current capacity, and TO-92-3 package compatibility. While the voltage rating is reduced to 45 V, this specification is acceptable for circuits operating within this threshold. Enhanced power dissipation (500 mW vs. 250 mW) and transition frequency (150MHz vs. 100MHz) provide improved performance margins. The DC current gain of 200 @ 2mA, 5V exceeds the original specification.

BC557BTA (onsemi) serves as a secondary substitute with identical electrical specifications to BC557BTF. This part is active, ROHS3 compliant, and available in substantial inventory (6,200 pcs). Packaging is specified as Cut Tape (CT), suitable for automated assembly processes.

BC557ATA (Fairchild Semiconductor) is a tertiary substitute option. This part is active and available (779 pcs inventory). Electrical specifications are equivalent to BC557BTA and BC557BTF with the exception of DC current gain, which is specified at 110 @ 2mA, 5V. This lower gain value may require circuit design adjustment in applications dependent on high current amplification.

All three substitute parts satisfy the mandatory compatibility criteria and are suitable for direct replacement in applications where the 2SA733-Q-AP operates at or below 45 V collector-emitter voltage.

Frequently Asked Questions (FAQ)

Q: Can BC557 series transistors directly replace the 2SA733-Q-AP in all applications?

A: BC557 series transistors are direct replacements for applications where the circuit operates at or below 45 V collector-emitter voltage. The 2SA733-Q-AP is rated for 50 V; therefore, circuits designed to utilize the full 50 V rating require verification that operating conditions remain within the 45 V specification of BC557 substitutes.

Q: What is the significance of the voltage rating difference between 50 V and 45 V?

A: The 2SA733-Q-AP is specified for maximum 50 V collector-emitter breakdown voltage, while BC557 series parts are rated at 45 V. This 5 V difference represents the maximum voltage stress the transistor can withstand. Circuits operating below 45 V experience no functional impact. Circuits designed to operate near or above 45 V require design review to ensure compliance with the lower BC557 rating.

Q: Are there differences in saturation voltage between the original and substitute parts?

A: Yes. The 2SA733-Q-AP specifies 300mV saturation voltage at 10mA base current and 100mA collector current. BC557 series parts specify 650mV saturation voltage at 5mA base current and 100mA collector current. The higher saturation voltage of BC557 parts may impact switching speed and power dissipation in saturation-mode applications. Circuit performance should be evaluated if saturation voltage is a critical design parameter.

Q: Do all substitute parts have identical DC current gain specifications?

A: No. BC557BTA and BC557BTF specify minimum DC current gain of 200 @ 2mA, 5V, while BC557ATA specifies 110 @ 2mA, 5V. The 2SA733-Q-AP specifies 135 @ 1mA, 6V. Gain specifications are measured at different operating points, making direct comparison difficult. Applications sensitive to current gain variation should be evaluated with the specific substitute part selected.

Q: Is the TO-92-3 package identical across all parts?

A: Yes. All substitute parts and the original 2SA733-Q-AP utilize the TO-226-3 / TO-92-3 (TO-226AA) formed leads package. Physical dimensions and lead configuration are compatible, permitting direct board-level substitution without layout modification.

Q: What is the impact of increased power dissipation rating on circuit performance?

A: The 2SA733-Q-AP is rated for 250 mW maximum power dissipation, while BC557 series substitutes are rated for 500 mW. The higher rating provides additional thermal margin and allows operation at higher power levels without exceeding absolute maximum ratings. This enhancement does not negatively impact circuit performance and may improve reliability in thermally constrained applications.

Q: Are all substitute parts RoHS3 compliant?

A: BC557BTA and BC557BTF are explicitly specified as ROHS3 compliant. BC557ATA RoHS status is not specified in the provided data. Applications requiring RoHS3 compliance should utilize BC557BTA or BC557BTF.

Q: What is the difference between Cut Tape (CT) and other packaging formats?

A: Cut Tape (CT) packaging indicates the component is supplied on continuous tape that is cut to length for shipment, typically used for automated pick-and-place assembly. This format differs from bulk or tube packaging but does not affect electrical performance or physical compatibility. Component selection between packaging formats depends on assembly process requirements.