ST901T NPN Darlington Transistor Equivalent & Substitute Parts

Part Overview

The ST901T is an NPN Darlington bipolar junction transistor manufactured by STMicroelectronics, designed for high-voltage switching and amplification applications. This component operates at a maximum collector-emitter breakdown voltage of 350 V with a maximum collector current of 4 A and maximum power dissipation of 100 W. The device is housed in a TO-220-3 through-hole package and maintains active product status with full RoHS3 compliance and REACH unaffected designation.

Substitute parts are identified when equivalent electrical and mechanical parameters allow direct replacement in circuit applications while maintaining functional performance within specified operating conditions.

Substiute Parts

ST901T

STMicroelectronicsIn Stock: 5460ST901T Datasheet

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MJE5742G

onsemiIn Stock: 8370MJE5742G Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the ST901T are identified based on the following critical electrical and mechanical parameters:

Substitution Criteria:

• Transistor type classification: NPN - Darlington configuration
• Package compatibility: TO-220-3 through-hole mounting
• Voltage rating: Collector-emitter breakdown voltage must equal or exceed 350 V
• Current capability: Collector current rating must equal or exceed 4 A
• Power dissipation: Maximum power rating must equal or exceed 100 W
• Compliance status: RoHS3 compliance and REACH unaffected designation

The MJE5742G manufactured by onsemi meets the mechanical packaging requirements (TO-220-3 through-hole) and exceeds the voltage (400 V) and current (8 A) specifications. However, the power dissipation rating of 2 W is significantly lower than the ST901T specification of 100 W, indicating this substitute is suitable only for applications where actual power dissipation remains within the MJE5742G thermal limits.

Parameter Comparison

Engineering Selection Recommendations

ST901T Selection: The ST901T is the primary component choice for applications requiring the specified 100 W power dissipation capability combined with 350 V voltage rating and 4 A current handling. This device maintains active product status with full RoHS3 compliance and REACH unaffected designation, ensuring regulatory compliance for current manufacturing standards.

MJE5742G Substitution Considerations: The MJE5742G provides equivalent mechanical compatibility through identical TO-220-3 through-hole packaging and exceeds voltage and current specifications. The device maintains active product status with RoHS3 compliance and REACH unaffected designation. However, the maximum power dissipation of 2 W represents a significant reduction from the ST901T specification of 100 W. This substitute is applicable only in circuits where thermal analysis confirms actual power dissipation remains within 2 W limits. The lower DC current gain (200 vs. 1800) and higher saturation voltage (3V vs. 2V) at specified test conditions indicate different electrical characteristics that may affect circuit performance in high-gain or low-loss applications.

Frequently Asked Questions (FAQ)

Q: Can the MJE5742G directly replace the ST901T in all applications?

A: Direct replacement is limited by power dissipation capability. The MJE5742G maximum power rating of 2 W is substantially lower than the ST901T specification of 100 W. Substitution is valid only when circuit analysis confirms actual power dissipation operates within the 2 W limit. Voltage and current specifications of the MJE5742G exceed ST901T requirements.

Q: Are both devices compatible with the same PCB footprint?

A: Yes. Both the ST901T and MJE5742G use identical TO-220-3 through-hole packaging, providing mechanical and thermal interface compatibility with standard TO-220 PCB layouts and heatsink mounting hardware.

Q: What is the significance of the DC current gain difference between these devices?

A: The ST901T specifies a minimum DC current gain (hFE) of 1800 at 2A and 2V, while the MJE5742G specifies 200 at 2A and 5V. This difference affects base drive requirements and circuit gain characteristics. Applications requiring high current gain benefit from the ST901T specification.

Q: Do both devices meet current regulatory compliance requirements?

A: Yes. Both the ST901T and MJE5742G maintain RoHS3 compliance and REACH unaffected designation, meeting current regulatory standards for electronic component manufacturing and distribution.

Q: What thermal considerations apply to substitution?

A: The TO-220-3 package provides identical thermal interface for both devices. However, the MJE5742G 2 W power limit requires lower junction temperatures than the ST901T 100 W specification. Thermal management design must account for the reduced power dissipation capability of the substitute device.

Q: Are there differences in saturation voltage that affect circuit design?

A: Yes. The ST901T specifies 2V saturation voltage at 20mA base current and 2A collector current, while the MJE5742G specifies 3V at 400mA base current and 8A collector current. Higher saturation voltage in the MJE5742G increases power loss in switching applications and may affect circuit performance in low-voltage designs.