STSA851-AP Equivalent & Substitute Parts

Part Overview

The STSA851-AP is an NPN bipolar junction transistor manufactured by STMicroelectronics, rated for 60 V collector-emitter breakdown voltage and 5 A maximum collector current. This device is packaged in TO-92AP through-hole configuration and is designed for general-purpose switching and amplification applications. The STSA851-AP is classified as obsolete, making identification of functionally equivalent active alternatives necessary for ongoing design support and procurement continuity.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	60	V
Current - Collector (Ic) (Max)	5	A
Power - Max	1.1	W
Frequency - Transition	130	MHz
Vce Saturation (Max) @ Ib, Ic	450 mV @ 200 mA, 5 A	—
DC Current Gain (hFE) (Min) @ Ic, Vce	150 @ 2 A, 1 V	—
Mounting Type	Through Hole	—
Package / Case	TO-226-3, TO-92-3 (TO-226AA)	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the STSA851-AP is determined by matching the following critical electrical parameters: NPN transistor type, maximum collector-emitter breakdown voltage (60 V minimum), maximum collector current (5 A minimum), and through-hole mounting compatibility. The substitute parts identified maintain these core specifications while offering active product status and improved availability.

The three substitute parts are grouped as follows:

Primary Substitute (Electrical and Mechanical Match): ZTX851STZ matches the STSA851-AP across all critical electrical parameters: 60 V breakdown voltage, 5 A collector current, 130 MHz transition frequency, and 1.2 W power rating. This part is packaged in E-Line (TO-92 compatible) configuration, maintaining through-hole mounting compatibility.

Secondary Substitutes (Partial Parameter Match): ZTX1053ASTZ and ZTX1049ASTZ provide alternative solutions for applications where specific electrical parameters can be relaxed. ZTX1053ASTZ offers higher breakdown voltage (75 V) but reduced collector current (3 A). ZTX1049ASTZ provides lower breakdown voltage (25 V) but maintains 4 A collector current capability.

Parameter Comparison

Parameter	STSA851-AP	ZTX851STZ	ZTX1053ASTZ	ZTX1049ASTZ
Transistor Type	NPN	NPN	NPN	NPN
Voltage - Collector Emitter Breakdown (Max)	60 V	60 V	75 V	25 V
Current - Collector (Ic) (Max)	5 A	5 A	3 A	4 A
Power - Max	1.1 W	1.2 W	1 W	1 W
Frequency - Transition	130 MHz	130 MHz	140 MHz	180 MHz
Vce Saturation (Max) @ Ib, Ic	450 mV @ 200 mA, 5 A	250 mV @ 200 mA, 5 A	350 mV @ 100 mA, 3 A	220 mV @ 50 mA, 4 A
DC Current Gain (hFE) (Min) @ Ic, Vce	150 @ 2 A, 1 V	100 @ 2 A, 1 V	300 @ 1 A, 2 V	300 @ 1 A, 2 V
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	TO-226-3, TO-92-3	E-Line-3 (TO-92 compatible)	E-Line-3 (TO-92 compatible)	E-Line-3 (TO-92 compatible)
Product Status	Obsolete	Active	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

ZTX851STZ is the primary recommended substitute for the STSA851-AP. This part maintains identical electrical specifications (60 V breakdown voltage, 5 A collector current, 130 MHz transition frequency) and is packaged in E-Line (TO-92 compatible) configuration, ensuring direct mechanical compatibility with existing through-hole PCB layouts. The ZTX851STZ is manufactured by Diodes Incorporated with active product status, ensuring long-term availability and supply chain stability. Both parts are ROHS3 compliant and carry identical ECCN and HTSUS classifications.

ZTX1053ASTZ is suitable for applications where collector current requirements do not exceed 3 A and higher breakdown voltage (75 V) provides design margin. This part offers improved transition frequency (140 MHz) and lower saturation voltage characteristics.

ZTX1049ASTZ is applicable only to circuits operating at collector-emitter voltages not exceeding 25 V. This part provides the highest transition frequency (180 MHz) and lowest saturation voltage but is not suitable for the full 60 V rating of the original STSA851-AP.

All substitute parts are ROHS3 compliant and carry REACH Unaffected status, matching the regulatory compliance profile of the original device.

Frequently Asked Questions (FAQ)

Q: Can ZTX851STZ be used as a direct replacement for STSA851-AP in all applications?

A: ZTX851STZ is electrically equivalent to STSA851-AP across all critical parameters (60 V breakdown voltage, 5 A collector current, 130 MHz transition frequency). The E-Line (TO-92 compatible) package maintains through-hole mounting compatibility. Direct substitution is appropriate for applications operating within the specified electrical ratings.

Q: What is the difference between TO-92AP and E-Line (TO-92 compatible) packaging?

A: Both packages are through-hole configurations with compatible lead spacing and pin assignments. TO-92AP is the original STMicroelectronics package designation, while E-Line is the Diodes Incorporated equivalent package. Both are suitable for standard through-hole PCB assembly without modification.

Q: Why is ZTX1049ASTZ listed as a substitute if it has only 25 V breakdown voltage?

A: ZTX1049ASTZ is listed as a substitute for applications where the circuit operates at voltages below 25 V. It is not suitable for circuits requiring the full 60 V rating of the STSA851-AP. Selection of this part requires verification that the application does not exceed 25 V collector-emitter voltage.

Q: Are all substitute parts RoHS compliant?

A: Yes. STSA851-AP, ZTX851STZ, ZTX1053ASTZ, and ZTX1049ASTZ are all ROHS3 compliant. All parts carry REACH Unaffected status and identical ECCN (EAR99) and HTSUS (8541.29.0075) classifications.

Q: What is the moisture sensitivity level (MSL) difference between the original and substitute parts?

A: STSA851-AP carries MSL 3 (168 Hours). ZTX851STZ, ZTX1053ASTZ, and ZTX1049ASTZ all carry MSL 1 (Unlimited), indicating superior moisture resistance and less stringent storage requirements for the substitute parts.

Q: Can ZTX1053ASTZ be used in place of STSA851-AP for 5 A applications?

A: No. ZTX1053ASTZ is rated for maximum 3 A collector current, which is insufficient for applications requiring the full 5 A capability of STSA851-AP. This part is suitable only for circuits operating at 3 A or below.

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