2SA844-C-AP Equivalent & Substitute Parts

Part Overview

The 2SA844-C-AP is a PNP bipolar junction transistor manufactured by Micro Commercial Co, designed for small-signal switching and amplification applications. Specified for 55 V collector-emitter breakdown voltage, 100 mA maximum collector current, and 300 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)	55	V
Power - Max	300	mW
Frequency - Transition	200	MHz
Operating Temperature (TJ)	150	°C
Mounting Type	Through Hole	—
Package / Case	TO-92-3	—

Substitute Part Grouping Explanation

Substitution of the 2SA844-C-AP is determined by the following critical parameters:

Mandatory Compatibility Criteria:

Transistor Type: PNP (all substitutes must be PNP configuration)
Current - Collector (Ic) Max: 100 mA (substitutes must support this rating)
Mounting Type: Through Hole (physical installation compatibility)
Package / Case: TO-92-3 (mechanical and pin compatibility)
Operating Temperature: 150°C (thermal operating range)

Allowable Parameter Variations:

Voltage - Collector Emitter Breakdown: Substitutes rated at 45 V or 65 V are acceptable, as these ratings exceed or match the 55 V requirement within the same device family
Power - Max: Substitutes rated at 500 mW exceed the 300 mW specification and are acceptable
Frequency - Transition: Substitutes rated at 150 MHz are acceptable for applications not requiring the full 200 MHz bandwidth
DC Current Gain (hFE): Variations in gain specifications are acceptable provided minimum gain meets application requirements

All identified substitutes are active products with current manufacturing status and RoHS3 compliance, addressing the obsolescence of the original 2SA844-C-AP.

Parameter Comparison

Parameter	2SA844-C-AP	BC556BTA	BC557ATA	BC557BTA	BC557BTF
Manufacturer	Micro Commercial Co	Fairchild Semiconductor	Fairchild Semiconductor	onsemi	onsemi
Transistor Type	PNP	PNP	PNP	PNP	PNP
Current - Collector (Ic) Max	100 mA	100 mA	100 mA	100 mA	100 mA
Voltage - Collector Emitter Breakdown (Max)	55 V	65 V	45 V	45 V	45 V
Vce Saturation (Max) @ Ib, Ic	500mV @ 1mA, 10mA	650mV @ 5mA, 100mA	650mV @ 5mA, 100mA	650mV @ 5mA, 100mA	650mV @ 5mA, 100mA
Current - Collector Cutoff (Max)	100nA (ICBO)	15nA (ICBO)	15nA (ICBO)	15nA (ICBO)	15nA (ICBO)
DC Current Gain (hFE) (Min) @ Ic, Vce	160 @ 2mA, 12V	200 @ 2mA, 5V	110 @ 2mA, 5V	200 @ 2mA, 5V	200 @ 2mA, 5V
Power - Max	300 mW	500 mW	500 mW	500 mW	500 mW
Frequency - Transition	200 MHz	150 MHz	150 MHz	150 MHz	150 MHz
Operating Temperature (TJ)	150°C	150°C	150°C	150°C	150°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	TO-92-3	TO-92-3	TO-92-3	TO-92-3	TO-92-3
Product Status	Obsolete	Active	Active	Active	Active
RoHS Status	ROHS3 Compliant	Not specified	Not specified	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

BC556BTA (Fairchild Semiconductor)

Highest voltage rating at 65 V, providing maximum headroom for applications with voltage transients
500 mW power rating exceeds original specification
Active product status ensures long-term availability
Suitable for designs requiring enhanced voltage margin

BC557ATA (Fairchild Semiconductor)

Lowest voltage rating at 45 V; suitable only for applications where 55 V breakdown voltage is not a critical requirement
500 mW power rating provides design margin
Active product status ensures availability
Minimum DC current gain of 110 @ 2mA, 5V is lower than original specification

BC557BTA (onsemi)

45 V voltage rating; suitable for applications not requiring full 55 V breakdown voltage
500 mW power rating exceeds original specification
Active product status with ROHS3 compliance
DC current gain of 200 @ 2mA, 5V exceeds original specification
Cut Tape packaging available

BC557BTF (onsemi)

45 V voltage rating; suitable for applications not requiring full 55 V breakdown voltage
500 mW power rating exceeds original specification
Active product status with ROHS3 compliance
DC current gain of 200 @ 2mA, 5V exceeds original specification
Highest inventory availability (41,626 pcs)
Cut Tape packaging available

For applications requiring the full 55 V collector-emitter breakdown voltage specification, BC556BTA is the appropriate substitute. For applications operating below 45 V, BC557BTA or BC557BTF provide equivalent functionality with enhanced power ratings and active manufacturing status.

Frequently Asked Questions (FAQ)

Q: Can BC557BTA or BC557BTF be used in place of 2SA844-C-AP in all applications?

A: BC557BTA and BC557BTF are suitable substitutes for applications where the collector-emitter voltage does not exceed 45 V. The original 2SA844-C-AP is rated for 55 V breakdown voltage. If the application requires operation at voltages between 45 V and 55 V, BC556BTA is the appropriate substitute.

Q: What is the difference between BC557BTA and BC557BTF?

A: BC557BTA and BC557BTF are functionally identical in electrical specifications. Both are manufactured by onsemi, rated for 45 V, 100 mA, and 500 mW. The primary difference is packaging format: BC557BTA is supplied in Cut Tape (CT) format, while BC557BTF is also supplied in Cut Tape (CT) format. Both are ROHS3 compliant and have identical electrical characteristics.

Q: Is the 150 MHz transition frequency of substitute parts adequate if the original part specifies 200 MHz?

A: The 150 MHz transition frequency of substitute parts is lower than the original 200 MHz specification. Substitutes are suitable for applications where the signal frequency does not approach the transition frequency limit. For applications requiring operation near or above 150 MHz, the original 2SA844-C-AP specifications should be verified against actual circuit requirements.

Q: Are all substitute parts RoHS3 compliant?

A: BC557BTA and BC557BTF are explicitly specified as ROHS3 compliant. BC556BTA and BC557ATA do not have RoHS status specified in the provided data. For applications requiring RoHS3 compliance certification, BC557BTA or BC557BTF are the recommended substitutes.

Q: What is the physical compatibility between 2SA844-C-AP and the substitute parts?

A: All substitute parts use the TO-92-3 package with formed leads, identical to the original 2SA844-C-AP. Physical pin configuration and through-hole mounting are compatible. Direct mechanical substitution is possible without PCB modification.

Q: How do the saturation voltage characteristics compare?

A: The original 2SA844-C-AP specifies 500 mV saturation voltage at 1 mA base current and 10 mA collector current. All substitute parts specify 650 mV saturation voltage at 5 mA base current and 100 mA collector current. These measurements are taken at different operating points, making direct comparison inappropriate. Saturation voltage performance should be verified against specific application requirements.

Q: Which substitute part has the best availability?

A: BC557BTF has the highest inventory availability at 41,626 pieces in stock, followed by BC557BTA at 6,200 pieces. BC556BTA has 18,244 pieces available. BC557ATA has the lowest availability at 779 pieces.

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