BD438S Equivalent & Substitute Parts

Part Overview

The BD438S is a PNP bipolar junction transistor manufactured by onsemi, rated for 45V collector-emitter breakdown voltage and 4A maximum collector current. This device is packaged in TO-126-3 configuration for through-hole mounting applications. The BD438S is currently in Last Time Buy status, indicating discontinued production. Identifying equivalent substitute parts is necessary to maintain design continuity and ensure component availability for ongoing production and repair applications.

Key Parameters

Parameter	Value	Unit
Transistor Type	PNP	—
Current - Collector (Ic) (Max)	4	A
Voltage - Collector Emitter Breakdown (Max)	45	V
Vce Saturation (Max) @ Ib, Ic	600mV @ 200mA, 2A	—
Current - Collector Cutoff (Max)	100	µA
DC Current Gain (hFE) (Min) @ Ic, Vce	30 @ 10mA, 5V	—
Power - Max	36	W
Frequency - Transition	3	MHz
Operating Temperature (TJ)	150	°C
Mounting Type	Through Hole	—

Substitute Part Grouping Explanation

Substitution of the BD438S is determined by electrical and mechanical parameter equivalence. The critical parameters that define substitutability are:

Transistor Type: PNP configuration
Current Rating: 4A maximum collector current
Voltage Rating: 45V collector-emitter breakdown voltage
Power Dissipation: 36W maximum
Saturation Characteristics: 600mV @ 200mA, 2A
Current Gain: Minimum 30 hFE @ 10mA, 5V
Transition Frequency: 3MHz
Mounting Configuration: Through-hole technology
Temperature Rating: 150°C maximum junction temperature

The BD438 from STMicroelectronics meets all electrical specifications identical to the BD438S. Although packaged in SOT-32-3 instead of TO-126-3, both packages are through-hole configurations with compatible pin assignments for the base product number BD438. This packaging difference does not affect electrical performance or functional substitutability.

Parameter Comparison

Parameter	BD438S (onsemi)	BD438 (STMicroelectronics)	Match
Transistor Type	PNP	PNP	✓
Current - Collector (Ic) (Max)	4 A	4 A	✓
Voltage - Collector Emitter Breakdown (Max)	45 V	45 V	✓
Vce Saturation (Max) @ Ib, Ic	600mV @ 200mA, 2A	600mV @ 200mA, 2A	✓
Current - Collector Cutoff (Max)	100 µA	100 µA	✓
DC Current Gain (hFE) (Min) @ Ic, Vce	30 @ 10mA, 5V	30 @ 10mA, 5V	✓
Power - Max	36 W	36 W	✓
Frequency - Transition	3 MHz	3 MHz	✓
Operating Temperature (TJ)	150 °C	150 °C	✓
Mounting Type	Through Hole	Through Hole	✓
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	✓
REACH Status	REACH Unaffected	REACH Unaffected	✓
ECCN	EAR99	EAR99	✓
HTSUS	8541.29.0095	8541.29.0095	✓

Engineering Selection Recommendations

The BD438 manufactured by STMicroelectronics is a direct electrical equivalent to the BD438S. All critical electrical parameters, including current rating, voltage rating, power dissipation, saturation characteristics, and frequency response, are identical.

The BD438S is designated Last Time Buy status, indicating production discontinuation. The STMicroelectronics BD438 is listed as Active product status, ensuring continued availability and supply chain reliability.

Both parts maintain ROHS3 compliance and REACH Unaffected status, satisfying regulatory requirements for new designs and production environments. The ECCN classification and HTSUS code are identical, confirming export and tariff classification equivalence.

The packaging difference between TO-126-3 (BD438S) and SOT-32-3 (BD438) does not affect electrical performance. Both are through-hole packages with compatible pin configurations for the BD438 base product number. PCB layout modifications may be required to accommodate the different package footprint.

Frequently Asked Questions (FAQ)

Q: Can the BD438 from STMicroelectronics directly replace the BD438S in existing designs?

A: Yes. All electrical specifications are identical, including current rating, voltage rating, power dissipation, saturation characteristics, and frequency response. The devices are electrically interchangeable. Physical PCB layout modifications are required due to package footprint differences between TO-126-3 and SOT-32-3.

Q: What is the difference between TO-126-3 and SOT-32-3 packages?

A: Both are through-hole packages with three leads. TO-126-3 and SOT-32-3 have different physical dimensions and lead spacing. Verification of PCB footprint compatibility is necessary before component substitution.

Q: Are there compliance or regulatory differences between the BD438S and BD438?

A: No. Both parts are ROHS3 compliant, REACH Unaffected, classified as EAR99 for export control, and share the same HTSUS tariff code 8541.29.0095.

Q: Why is the BD438S listed as Last Time Buy?

A: Last Time Buy status indicates the manufacturer (onsemi) has discontinued production. The BD438 from STMicroelectronics remains in Active production status, providing continued component availability.

Q: What parameters must match for substitution to be valid?

A: Transistor type (PNP), maximum collector current (4A), collector-emitter breakdown voltage (45V), power rating (36W), saturation voltage (600mV @ 200mA, 2A), minimum current gain (30 hFE @ 10mA, 5V), transition frequency (3MHz), and operating temperature (150°C) must all be identical.

Q: Is the DC current gain specification identical between both parts?

A: Yes. Both the BD438S and BD438 specify a minimum DC current gain (hFE) of 30 measured at 10mA collector current and 5V collector-emitter voltage.

Q: Can the BD438 be used in high-frequency applications?

A: Both devices have a transition frequency of 3MHz. Applications requiring higher frequency response require evaluation of alternative transistor types with higher fT specifications.

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