BD440 Equivalent & Substitute Parts

Part Overview

The BD440 is a PNP bipolar junction transistor manufactured by onsemi, rated for 60 V collector-emitter breakdown voltage and 4 A maximum collector current. The device is packaged in TO-126 (TO-225AA) through-hole configuration and is designed for general-purpose switching and amplification applications with a maximum power dissipation of 36 W.

The BD440 is classified as obsolete. Equivalent and substitute parts are necessary to maintain design continuity and ensure component availability for new production runs, repairs, and legacy system support.

Key Parameters

Parameter	Value	Unit
Transistor Type	PNP	—
Current - Collector (Ic) Max	4	A
Voltage - Collector Emitter Breakdown (Max)	60	V
Power - Max	36	W
Frequency - Transition	3	MHz
Mounting Type	Through Hole	—
Operating Temperature Range	-55 to 150	°C

Substitute Part Grouping Explanation

Substitution of the BD440 is determined by the following critical parameters:

Mandatory Matching Criteria:

Transistor polarity: PNP
Collector current rating: 4 A minimum
Power dissipation: 36 W minimum
Transition frequency: 3 MHz minimum
Mounting type: Through hole
Package compatibility: TO-126 or equivalent footprint

Allowable Variation:

Collector-emitter breakdown voltage may be lower than 60 V, provided the application voltage requirement does not exceed the substitute part rating
DC current gain (hFE) and saturation voltage may differ within acceptable design margins
Operating temperature range may be narrower than the original specification

The BD438 meets the mandatory criteria for collector current, power dissipation, transition frequency, and through-hole mounting. However, the collector-emitter breakdown voltage is rated at 45 V, which is lower than the BD440. This substitution is valid only for applications where the maximum operating voltage does not exceed 45 V.

Parameter Comparison

Parameter	BD440 (onsemi)	BD438 (STMicroelectronics)	Unit
Transistor Type	PNP	PNP	—
Current - Collector (Ic) Max	4	4	A
Voltage - Collector Emitter Breakdown (Max)	60	45	V
Vce Saturation (Max)	800 mV @ 300 mA, 3 A	600 mV @ 200 mA, 2 A	—
Current - Collector Cutoff (Max)	100	100	µA
DC Current Gain (hFE) Min	40 @ 500 mA, 1 V	30 @ 10 mA, 5 V	—
Power - Max	36	36	W
Frequency - Transition	3	3	MHz
Operating Temperature (TJ)	-55 to 150	Up to 150	°C
Mounting Type	Through Hole	Through Hole	—
Package / Case	TO-126	SOT-32-3	—
Product Status	Obsolete	Active	—
RoHS Status	Non-compliant	ROHS3 Compliant	—

Engineering Selection Recommendations

BD438 as Substitute for BD440:

The BD438 is an active, ROHS3-compliant alternative to the obsolete BD440. Both devices share identical collector current (4 A), power dissipation (36 W), and transition frequency (3 MHz) ratings. The primary design consideration is the reduced collector-emitter breakdown voltage of the BD438 (45 V versus 60 V).

Selection of the BD438 is appropriate for applications where the maximum supply voltage or peak transient voltage does not exceed 45 V. The improved saturation voltage characteristics (600 mV versus 800 mV) of the BD438 may provide enhanced switching efficiency in low-voltage applications.

The BD438 carries ROHS3 compliance, whereas the BD440 is non-compliant. For new designs or production requiring regulatory compliance, the BD438 is the preferred selection.

Package differences exist between the two devices (TO-126 versus SOT-32-3). Physical board layout and thermal management considerations must be evaluated during design integration.

Frequently Asked Questions (FAQ)

Q: Can the BD438 directly replace the BD440 in all applications?

A: The BD438 is a functional substitute only for applications where the maximum operating voltage does not exceed 45 V. The BD440 is rated for 60 V operation. If the circuit operates above 45 V, the BD438 is not suitable.

Q: What are the package differences between BD440 and BD438?

A: The BD440 uses TO-126 (TO-225AA) packaging, while the BD438 uses SOT-32-3 packaging. Both are through-hole mount types, but physical dimensions and pin spacing differ. PCB layout modifications may be required.

Q: Are there compliance differences between these parts?

A: Yes. The BD440 is RoHS non-compliant, while the BD438 is ROHS3 compliant. For applications requiring regulatory compliance, the BD438 is the appropriate selection.

Q: How do the DC current gain specifications compare?

A: The BD440 specifies a minimum hFE of 40 at 500 mA and 1 V, while the BD438 specifies a minimum hFE of 30 at 10 mA and 5 V. These measurements are taken at different operating points and are not directly comparable. Circuit design must account for the actual operating conditions.

Q: What is the significance of the saturation voltage difference?

A: The BD438 exhibits lower saturation voltage (600 mV) compared to the BD440 (800 mV) at their respective test conditions. Lower saturation voltage reduces power dissipation during saturation and improves switching efficiency in low-voltage applications.

Q: Is the BD438 available in the same TO-126 package as the BD440?

A: No. The BD438 is supplied in SOT-32-3 packaging. If TO-126 packaging is required, alternative substitutes must be evaluated or the original BD440 inventory must be sourced.

Q: What is the operating temperature range for the BD438?

A: The BD438 is rated for operation up to 150°C junction temperature. The lower temperature limit is not specified in the provided data. The BD440 specifies -55°C to 150°C. Verify the minimum operating temperature requirement for your application.

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