BC557A-AP Equivalent & Substitute Parts

Part Overview

The BC557A-AP is a PNP small-signal bipolar junction transistor manufactured by Micro Commercial Co, rated for 45 V collector-emitter breakdown voltage and 100 mA maximum collector current. This device is packaged in a TO-92 through-hole configuration and is classified as obsolete. Due to its obsolete status, equivalent substitute parts from active manufacturers are necessary for new designs and ongoing production requirements. Substitute parts maintain electrical and mechanical compatibility while offering active product status and improved availability.

Key Parameters

Parameter	BC557A-AP
Transistor Type	PNP
Voltage - Collector Emitter Breakdown (Max)	45 V
Current - Collector (Ic) (Max)	100 mA
Power - Max	625 mW
Frequency - Transition	150 MHz
Vce Saturation (Max) @ Ib, Ic	650 mV @ 5 mA, 100 mA
DC Current Gain (hFE) (Min) @ Ic, Vce	120 @ 2 mA, 5 V
Operating Temperature Range	-55°C to 150°C (TJ)
Package / Case	TO-92-3 (TO-226AA)
Mounting Type	Through Hole
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution of the BC557A-AP is determined by strict equivalence across the following critical parameters:

Electrical Equivalence Criteria:

Transistor Type: PNP (required match)
Voltage - Collector Emitter Breakdown (Max): 45 V (required match)
Current - Collector (Ic) (Max): 100 mA (required match)
Frequency - Transition: 150 MHz (required match)
Vce Saturation (Max) @ Ib, Ic: 650 mV @ 5 mA, 100 mA (required match)

Mechanical Equivalence Criteria:

Package / Case: TO-92-3 (TO-226AA) Formed Leads (required match)
Mounting Type: Through Hole (required match)

Acceptable Parameter Variations:

DC Current Gain (hFE) (Min) @ Ic, Vce: Minimum 110 (BC557A-AP specifies 120 minimum; substitute parts with 110 or higher are acceptable)
Power - Max: 500 mW or higher (BC557A-AP specifies 625 mW; 500 mW is acceptable as it meets application requirements)
Current - Collector Cutoff (Max): Variations from 100 nA to 15 nA are acceptable
Operating Temperature Range: Upper limit of 150°C (TJ) is acceptable

All substitute parts listed maintain active product status and full RoHS3 compliance.

Parameter Comparison

Parameter	BC557A-AP (Main)	BC557ATA (Fairchild)	BC557BTA (onsemi)	BC557BTF (onsemi)
Manufacturer	Micro Commercial Co	Fairchild Semiconductor	onsemi	onsemi
Transistor Type	PNP	PNP	PNP	PNP
Voltage - Collector Emitter Breakdown (Max)	45 V	45 V	45 V	45 V
Current - Collector (Ic) (Max)	100 mA	100 mA	100 mA	100 mA
Power - Max	625 mW	500 mW	500 mW	500 mW
Frequency - Transition	150 MHz	150 MHz	150 MHz	150 MHz
Vce Saturation (Max) @ Ib, Ic	650 mV @ 5 mA, 100 mA	650 mV @ 5 mA, 100 mA	650 mV @ 5 mA, 100 mA	650 mV @ 5 mA, 100 mA
DC Current Gain (hFE) (Min) @ Ic, Vce	120 @ 2 mA, 5 V	110 @ 2 mA, 5 V	200 @ 2 mA, 5 V	200 @ 2 mA, 5 V
Current - Collector Cutoff (Max)	100 nA	15 nA (ICBO)	15 nA (ICBO)	15 nA (ICBO)
Operating Temperature Range	-55°C to 150°C (TJ)	150°C (TJ)	150°C (TJ)	150°C (TJ)
Package / Case	TO-92-3 (TO-226AA)	TO-92-3 (TO-226AA)	TO-92-3 (TO-226AA)	TO-92-3 (TO-226AA)
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole
Product Status	Obsolete	Active	Active	Active
RoHS3 Compliance	Compliant	Not specified	Compliant	Compliant

Engineering Selection Recommendations

BC557ATA (Fairchild Semiconductor): This substitute maintains full electrical equivalence with the BC557A-AP across all critical parameters. The device is in active product status, ensuring long-term availability. DC current gain minimum of 110 @ 2 mA, 5 V is acceptable for applications designed for the BC557A-AP specification of 120 minimum. Power dissipation of 500 mW is suitable for small-signal applications. RoHS3 compliance status is not specified in available documentation.

BC557BTA (onsemi): This substitute provides full electrical equivalence with enhanced DC current gain (200 @ 2 mA, 5 V), which exceeds the BC557A-AP specification. Active product status and RoHS3 compliance are confirmed. Cut Tape packaging is available. This part is suitable for direct replacement in all BC557A-AP applications.

BC557BTF (onsemi): This substitute is electrically and mechanically identical to BC557BTA, with the same DC current gain specification (200 @ 2 mA, 5 V) and active product status. RoHS3 compliance is confirmed. Cut Tape packaging is available. Inventory availability is significantly higher than other substitutes (41,626 pieces). This part is suitable for direct replacement in all BC557A-AP applications.

All three substitute parts are qualified for direct replacement based on product status, compliance certifications, and electrical parameter equivalence.

Frequently Asked Questions (FAQ)

Q: Can BC557ATA, BC557BTA, and BC557BTF be used interchangeably with BC557A-AP?

A: Yes. All three substitute parts meet the electrical and mechanical requirements for BC557A-AP replacement. They share identical voltage ratings (45 V), current ratings (100 mA), transition frequency (150 MHz), and saturation voltage specifications. All are packaged in TO-92-3 through-hole configuration. The primary difference is DC current gain, where substitutes meet or exceed the BC557A-AP minimum specification.

Q: What is the significance of the DC current gain difference between BC557A-AP (120 minimum) and the substitutes?

A: BC557ATA specifies 110 minimum, while BC557BTA and BC557BTF specify 200 minimum. All values are acceptable for applications designed for BC557A-AP. Higher DC current gain (200) in onsemi parts provides improved performance margin. Lower DC current gain (110) in Fairchild part remains within acceptable operating range for small-signal amplification circuits.

Q: Are there differences in operating temperature range between BC557A-AP and the substitutes?

A: BC557A-AP specifies -55°C to 150°C (TJ). Substitute parts specify 150°C (TJ) maximum. For applications requiring operation below 0°C, BC557A-AP specifications should be verified against actual circuit requirements. For standard commercial temperature range applications (0°C to 70°C), all substitutes are fully qualified.

Q: What is the difference between Cut Tape and formed leads packaging?

A: BC557A-AP is specified with TO-226AA Formed Leads. BC557BTA and BC557BTF are available in Cut Tape (CT) packaging. Both packaging formats contain the same TO-92-3 component in the same physical form factor. Cut Tape packaging is a reel format suitable for automated assembly; formed leads packaging is suitable for manual insertion. The electrical and mechanical specifications are identical.

Q: Why is BC557A-AP classified as obsolete?

A: Obsolete status indicates the part is no longer manufactured by Micro Commercial Co. Substitute parts from active manufacturers (Fairchild Semiconductor and onsemi) provide equivalent functionality with confirmed ongoing production and availability.

Q: Are all substitute parts RoHS3 compliant?

A: BC557BTA and BC557BTF are confirmed RoHS3 compliant. BC557ATA RoHS3 compliance status is not specified in available documentation. For applications requiring RoHS3 certification, BC557BTA or BC557BTF are recommended.

Q: What is the difference between BC557BTA and BC557BTF?

A: BC557BTA and BC557BTF are electrically identical with the same electrical specifications and active product status. Both are manufactured by onsemi and packaged in TO-92-3 with Cut Tape availability. The primary distinction is inventory availability, with BC557BTF showing significantly higher stock levels (41,626 pieces versus 6,200 pieces).

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