STX715 Equivalent & Substitute Parts

Part Overview

The STX715 is an NPN bipolar junction transistor manufactured by STMicroelectronics, rated for 80 V collector-emitter breakdown voltage and 1.5 A maximum collector current. The device is packaged in a TO-92-3 through-hole configuration and is designed for general-purpose switching and amplification applications with a maximum power dissipation of 900 mW.

The STX715 is classified as obsolete. Identifying equivalent and substitute parts is necessary to maintain design continuity, ensure supply chain availability, and support ongoing production or repair requirements for systems utilizing this component.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	80	V
Current - Collector (Ic) (Max)	1.5	A
Power - Max	900	mW
Frequency - Transition	50	MHz
Vce Saturation (Max)	500 mV @ 100 mA, 1 A	—
DC Current Gain (hFE) (Min)	40 @ 1 A, 2 V	—
Operating Temperature (Max)	150	°C
Package / Case	TO-92-3	—
Mounting Type	Through Hole	—

Substitute Part Grouping Explanation

Substitution of the STX715 is determined by electrical and mechanical compatibility across the following critical parameters:

Electrical Compatibility Criteria:

Transistor type must be NPN
Collector-emitter breakdown voltage must be greater than or equal to 80 V
Maximum collector current must be greater than or equal to 1.5 A
Maximum power dissipation must be greater than or equal to 900 mW
DC current gain (hFE) must support the intended bias conditions
Saturation voltage characteristics must be compatible with circuit requirements

Mechanical Compatibility Criteria:

Mounting type must be through-hole
Package must be physically compatible with PCB footprints designed for TO-92-3 or equivalent through-hole configurations

Compliance Criteria:

RoHS3 compliance required
REACH unaffected status required

The substitute parts identified below meet these criteria within the specified tolerances and operating conditions.

Parameter Comparison

Parameter	STX715 (Main)	BD139G (Substitute)	KSD1616AGBU (Substitute)
Manufacturer	STMicroelectronics	onsemi	onsemi
Transistor Type	NPN	NPN	NPN
Voltage - Collector Emitter Breakdown (Max)	80 V	80 V	60 V
Current - Collector (Ic) (Max)	1.5 A	1.5 A	1 A
Power - Max	900 mW	12.5 W	750 mW
Frequency - Transition	50 MHz	—	160 MHz
Vce Saturation (Max)	500 mV @ 100 mA, 1 A	500 mV @ 50 mA, 500 mA	300 mV @ 50 mA, 1 A
DC Current Gain (hFE) (Min)	40 @ 1 A, 2 V	40 @ 150 mA, 2 V	200 @ 100 mA, 2 V
Operating Temperature (Max)	150°C	150°C	150°C
Package / Case	TO-92-3	TO-126-3	TO-92-3
Mounting Type	Through Hole	Through Hole	Through Hole
Product Status	Obsolete	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
REACH Status	REACH Unaffected	REACH Unaffected	REACH Unaffected

Engineering Selection Recommendations

BD139G (onsemi): The BD139G is an active-status NPN transistor that matches the STX715 in collector-emitter breakdown voltage (80 V) and maximum collector current (1.5 A). The BD139G provides superior power dissipation capability (12.5 W versus 900 mW), making it suitable for applications requiring higher thermal headroom. The primary consideration is the package difference: BD139G uses TO-126-3 packaging, which has a larger footprint than the TO-92-3 package of the STX715. This substitution requires PCB layout modification. The BD139G is RoHS3 compliant and REACH unaffected, meeting regulatory requirements.

KSD1616AGBU (onsemi): The KSD1616AGBU is an active-status NPN transistor in TO-92-3 packaging, providing direct mechanical compatibility with the STX715. The KSD1616AGBU meets or exceeds the STX715 in several electrical parameters: DC current gain (200 versus 40), transition frequency (160 MHz versus 50 MHz), and saturation voltage performance (300 mV versus 500 mV). However, the KSD1616AGBU has reduced maximum collector-emitter breakdown voltage (60 V versus 80 V) and maximum collector current (1 A versus 1.5 A). This substitution is suitable for applications where the circuit operates below 60 V and requires collector currents not exceeding 1 A. The KSD1616AGBU is RoHS3 compliant and REACH unaffected.

Both substitute parts are active products with established supply availability, supporting long-term design continuity.

Frequently Asked Questions (FAQ)

Q: Can the BD139G directly replace the STX715 without PCB modifications?

A: No. The BD139G uses TO-126-3 packaging, which differs physically from the STX715's TO-92-3 package. The TO-126 package is larger and has a different pin configuration and footprint. PCB layout modifications are required for mechanical compatibility.

Q: Is the KSD1616AGBU suitable for all STX715 applications?

A: The KSD1616AGBU is suitable for applications where the circuit operates at collector-emitter voltages not exceeding 60 V and collector currents not exceeding 1 A. Applications requiring the full 80 V rating or 1.5 A current capability of the STX715 cannot use the KSD1616AGBU without circuit redesign.

Q: What are the key differences between the two substitute parts?

A: The BD139G offers higher power dissipation (12.5 W) and maintains the full 80 V / 1.5 A electrical ratings of the STX715 but requires package-level PCB changes. The KSD1616AGBU provides direct TO-92-3 package compatibility and superior frequency response but operates at reduced voltage and current ratings.

Q: Are both substitute parts RoHS3 compliant?

A: Yes. Both the BD139G and KSD1616AGBU are RoHS3 compliant and REACH unaffected, meeting current regulatory requirements for electronic components.

Q: Which substitute should be selected for a direct drop-in replacement?

A: The KSD1616AGBU provides direct mechanical compatibility through identical TO-92-3 packaging. However, electrical compatibility must be verified against the specific circuit requirements, particularly regarding the 60 V maximum breakdown voltage and 1 A maximum collector current limitations.

Q: What is the impact of the different saturation voltages on circuit performance?

A: Saturation voltage affects the voltage drop across the transistor in the saturated state. The KSD1616AGBU exhibits lower saturation voltage (300 mV) compared to the STX715 (500 mV), resulting in reduced power dissipation in saturated switching applications. The BD139G maintains the same saturation voltage specification as the STX715 at comparable test conditions.

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