2SA733-K-AP Equivalent & Substitute Parts

Part Overview

The 2SA733-K-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 and 250 mW power dissipation in a TO-92 through-hole package. The device is classified as obsolete, necessitating identification of active equivalent alternatives that maintain functional compatibility within specified electrical and mechanical parameters.

Key Parameters

Parameter	Value	Unit
Transistor Type	PNP	—
Current - Collector (Ic) Max	100	mA
Voltage - Collector Emitter Breakdown (Max)	50	V
Power - Max	250	mW
Frequency - Transition	100	MHz
Mounting Type	Through Hole	—
Package / Case	TO-92-3	—
Operating Temperature Range	-55 to 150	°C

Substitute Part Grouping Explanation

Substitution of the 2SA733-K-AP is determined by equivalence in the following critical parameters:

Mandatory Compatibility Parameters:

Transistor polarity: PNP
Maximum collector current: 100 mA
Package type: TO-92-3 through-hole
Mounting configuration: Through hole with formed leads

Acceptable Parameter Variations:

Collector-emitter breakdown voltage: Substitute parts rated at 45 V are acceptable for applications not requiring the full 50 V rating of the original device
Power dissipation: Substitute parts rated at 500 mW exceed the 250 mW requirement and provide enhanced thermal margin
Transition frequency: Substitute parts rated at 150 MHz exceed the 100 MHz specification
DC current gain (hFE): Variations in gain are acceptable provided the substitute operates within the specified collector current and voltage ranges

The BC557 series transistors (BC557ATA, BC557BTA, BC557BTF) satisfy all mandatory compatibility criteria and provide electrical performance within acceptable ranges for direct substitution.

Parameter Comparison

Parameter	2SA733-K-AP	BC557ATA	BC557BTA	BC557BTF	Unit
Manufacturer	Micro Commercial Co	Fairchild Semiconductor	onsemi	onsemi	—
Product Status	Obsolete	Active	Active	Active	—
Transistor Type	PNP	PNP	PNP	PNP	—
Current - Collector (Ic) Max	100	100	100	100	mA
Voltage - Collector Emitter Breakdown (Max)	50	45	45	45	V
Vce Saturation (Max) @ Ib, Ic	300mV @ 10mA, 100mA	650mV @ 5mA, 100mA	650mV @ 5mA, 100mA	650mV @ 5mA, 100mA	V
Current - Collector Cutoff (Max)	100	15	15	15	nA
DC Current Gain (hFE) Min @ Ic, Vce	300 @ 1mA, 6V	110 @ 2mA, 5V	200 @ 2mA, 5V	200 @ 2mA, 5V	—
Power - Max	250	500	500	500	mW
Frequency - Transition	100	150	150	150	MHz
Operating Temperature (TJ)	-55 to 150	150	150	150	°C
Package / Case	TO-92-3	TO-92-3	TO-92-3	TO-92-3	—
RoHS Status	ROHS3 Compliant	Not specified	ROHS3 Compliant	ROHS3 Compliant	—

Engineering Selection Recommendations

BC557BTF (onsemi) is the primary substitute for the 2SA733-K-AP. This device is active in production, ROHS3 compliant, and available in high inventory (41,626 pcs). The BC557BTF maintains PNP polarity, 100 mA collector current rating, and TO-92-3 package compatibility. The 45 V collector-emitter breakdown voltage is suitable for applications operating below 45 V. Enhanced power rating (500 mW vs. 250 mW) and transition frequency (150 MHz vs. 100 MHz) provide improved thermal and frequency performance margins.

BC557BTA (onsemi) serves as a secondary substitute with identical electrical specifications to BC557BTF, differentiated by packaging format (cut tape vs. alternative packaging). ROHS3 compliance and active production status support long-term availability. Inventory availability (6,200 pcs) is adequate for production requirements.

BC557ATA (Fairchild Semiconductor) is a tertiary option with active product status and ROHS3 compliance. The lower DC current gain specification (110 @ 2mA, 5V) compared to BC557BTA/BTF variants may require circuit verification in gain-sensitive applications. Inventory (779 pcs) is lower than onsemi alternatives.

All three substitute parts are electrically and mechanically compatible with the 2SA733-K-AP within the specified parameter ranges and application constraints.

Frequently Asked Questions (FAQ)

Q: Can BC557 series transistors directly replace the 2SA733-K-AP without circuit modification?

A: BC557 series transistors are pin-compatible and functionally equivalent for applications operating at collector-emitter voltages below 45 V. The identical TO-92-3 package and PNP polarity enable direct physical substitution. Applications requiring the full 50 V rating of the original device require voltage derating analysis.

Q: What is the significance of the 45 V vs. 50 V collector-emitter breakdown voltage difference?

A: The 2SA733-K-AP is rated for 50 V maximum collector-emitter breakdown voltage, while BC557 substitutes are rated at 45 V. For applications operating at voltages below 45 V, this difference is not significant. Applications requiring operation between 45 V and 50 V require alternative components or circuit redesign to operate within the 45 V limit.

Q: Are there differences in DC current gain between the substitute options?

A: Yes. BC557ATA specifies minimum hFE of 110 @ 2mA, 5V, while BC557BTA and BC557BTF specify minimum hFE of 200 @ 2mA, 5V. The 2SA733-K-AP specifies hFE of 300 @ 1mA, 6V. Circuits dependent on specific gain values require verification against the substitute device specifications. Higher gain variants (BC557BTA/BTF) provide closer performance to the original device.

Q: What is the impact of the 250 mW vs. 500 mW power rating difference?

A: The substitute parts are rated for 500 mW maximum power dissipation, double the 250 mW rating of the 2SA733-K-AP. This provides enhanced thermal margin and allows operation at higher power levels without thermal derating. For applications within the original 250 mW specification, the higher rating presents no disadvantage.

Q: Are all substitute parts ROHS3 compliant?

A: BC557BTA and BC557BTF are explicitly ROHS3 compliant. BC557ATA compliance status is not specified in the provided data. For applications requiring ROHS3 certification, BC557BTA or BC557BTF are recommended.

Q: What is the difference between BC557BTF and BC557BTA packaging?

A: Both devices are supplied in TO-92-3 package with formed leads. BC557BTF is supplied in cut tape (CT) format, while BC557BTA is also supplied in cut tape format. The electrical specifications are identical; packaging format selection depends on assembly process requirements.

Q: Can the 2SA733-K-AP be used interchangeably with BC557 devices in existing designs?

A: The 2SA733-K-AP is obsolete and no longer in production. BC557 series devices are active alternatives with compatible electrical and mechanical specifications. New designs should specify BC557 series transistors. Existing designs using 2SA733-K-AP can transition to BC557 series with verification that application voltage and gain requirements are satisfied by the substitute device specifications.

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