BULT118M Equivalent & Substitute Parts

Part Overview

The BULT118M is an NPN bipolar junction transistor manufactured by STMicroelectronics, rated for 400 V collector-emitter breakdown voltage and 2 A maximum collector current in a Through Hole SOT-32-3 package. This device is classified as obsolete, making identification of functionally equivalent alternatives necessary for ongoing design support and production continuity. The 45 W power rating and 150°C maximum junction temperature establish the thermal and electrical operating envelope for potential substitutes.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	400	V
Current - Collector (Ic) (Max)	2	A
Power - Max	45	W
Vce Saturation (Max) @ Ib, Ic	1.5V @ 400mA, 2A	—
DC Current Gain (hFE) (Min) @ Ic, Vce	10 @ 500mA, 5V	—
Operating Temperature (TJ)	150	°C
Mounting Type	Through Hole	—
Package / Case	TO-225AA, TO-126-3	—

Substitute Part Grouping Explanation

Substitution of the BULT118M is determined by the following critical electrical and mechanical parameters:

Voltage Rating: The substitute must maintain a minimum collector-emitter breakdown voltage of 400 V to ensure operation within the same voltage class.

Current Rating: The substitute must support the required collector current. The BULT118M specifies 2 A maximum; substitutes with equal or greater current capacity are acceptable.

Power Dissipation: The substitute must accommodate the thermal load. The BULT118M is rated for 45 W; substitutes with equal or greater power ratings are acceptable.

Saturation Characteristics: The Vce saturation voltage determines switching performance and power loss in saturated operation. Substitutes must operate within compatible saturation parameters.

DC Current Gain: The minimum hFE establishes base drive requirements. Substitutes must provide sufficient current gain for the intended circuit configuration.

Package Compatibility: Through Hole mounting and TO-126-3 package compatibility ensure mechanical and thermal interface compatibility.

Temperature Rating: The 150°C maximum junction temperature establishes the thermal operating limit.

The FJE3303H2TU meets the voltage and package requirements but operates at reduced current (1.5 A versus 2 A) and power (20 W versus 45 W), making it suitable only for applications within these lower ratings.

Parameter Comparison

Parameter	BULT118M	FJE3303H2TU	Unit
Transistor Type	NPN	NPN	—
Voltage - Collector Emitter Breakdown (Max)	400	400	V
Current - Collector (Ic) (Max)	2	1.5	A
Power - Max	45	20	W
Vce Saturation (Max) @ Ib, Ic	1.5V @ 400mA, 2A	3V @ 500mA, 1.5A	—
DC Current Gain (hFE) (Min) @ Ic, Vce	10 @ 500mA, 5V	14 @ 500mA, 2V	—
Operating Temperature (TJ)	150	150	°C
Mounting Type	Through Hole	Through Hole	—
Package / Case	TO-225AA, TO-126-3	TO-225AA, TO-126-3	—
Frequency - Transition	—	4	MHz

Engineering Selection Recommendations

BULT118M Status: The BULT118M is classified as obsolete. Designs requiring this component must transition to active alternatives to ensure long-term supply availability and manufacturing support.

FJE3303H2TU Suitability: The FJE3303H2TU is an active product from Fairchild Semiconductor with 8653 units in stock. It shares the 400 V voltage rating and Through Hole TO-126-3 package configuration with the BULT118M.

Current and Power Limitations: The FJE3303H2TU is rated for 1.5 A maximum collector current and 20 W maximum power dissipation, compared to the BULT118M's 2 A and 45 W ratings. Selection of the FJE3303H2TU is restricted to applications operating within these reduced electrical limits.

Saturation Performance: The FJE3303H2TU exhibits higher Vce saturation (3 V at 1.5 A) compared to the BULT118M (1.5 V at 2 A), resulting in increased power dissipation during saturated operation.

Compliance: Both devices are ROHS3 compliant and carry EAR99 ECCN classification, supporting equivalent regulatory and export compliance requirements.

Frequently Asked Questions (FAQ)

Q: Can the FJE3303H2TU directly replace the BULT118M in all applications?

A: No. The FJE3303H2TU operates at reduced current (1.5 A versus 2 A) and power (20 W versus 45 W) ratings. Direct substitution is limited to applications operating within these lower electrical specifications.

Q: What is the primary reason for seeking a substitute for the BULT118M?

A: The BULT118M is classified as obsolete. Substitution is necessary to maintain design continuity and ensure component availability for production and support.

Q: Are the packages mechanically compatible?

A: Yes. Both the BULT118M and FJE3303H2TU use Through Hole mounting with TO-126-3 package configuration, ensuring mechanical and thermal interface compatibility.

Q: How does the saturation voltage difference affect circuit performance?

A: The FJE3303H2TU exhibits higher Vce saturation (3 V) than the BULT118M (1.5 V). In saturated switching applications, this results in increased power dissipation and heat generation. Circuit thermal design must account for this difference.

Q: Are there voltage rating differences between these devices?

A: No. Both devices are rated for 400 V maximum collector-emitter breakdown voltage, ensuring equivalent voltage class operation.

Q: What is the impact of the 4 MHz transition frequency specification on the FJE3303H2TU?

A: The FJE3303H2TU specifies a 4 MHz transition frequency. This parameter is not provided for the BULT118M. Applications requiring specific frequency response characteristics must evaluate this specification against circuit requirements.

Q: Can the FJE3303H2TU be used in high-current applications originally designed for the BULT118M?

A: No. Applications requiring sustained collector currents above 1.5 A or power dissipation above 20 W exceed the FJE3303H2TU ratings and require alternative components.

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