BD434S Equivalent & Substitute Parts Reference

Part Overview

The BD434S is a PNP bipolar junction transistor manufactured by onsemi, rated for 22 V collector-emitter breakdown voltage and 4 A maximum collector current. This device is packaged in TO-126-3 through-hole configuration with a maximum power dissipation of 36 W and transition frequency of 3 MHz. The BD434S is classified as obsolete, necessitating identification of equivalent and substitute components for ongoing design requirements and production continuity.

Key Parameters

Parameter	Value	Unit
Transistor Type	PNP	—
Current - Collector (Ic) Max	4	A
Voltage - Collector Emitter Breakdown (Max)	22	V
Vce Saturation (Max)	500 mV @ 200 mA, 2 A	—
Current - Collector Cutoff (Max)	100	µA
DC Current Gain (hFE) Min	40 @ 10 mA, 5 V	—
Power - Max	36	W
Frequency - Transition	3	MHz
Operating Temperature (TJ)	150	°C
Mounting Type	Through Hole	—
Package / Case	TO-126-3	—
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the BD434S is determined by strict alignment of electrical and mechanical parameters within the PNP bipolar transistor category. The following criteria establish valid substitution relationships:

Primary Substitution Criteria:

Transistor type must be PNP
Collector current rating (Ic Max) must equal or exceed 4 A
Voltage rating (Vce breakdown) must equal or exceed 22 V
Power dissipation (P Max) must equal or exceed 36 W
Transition frequency must equal or exceed 3 MHz
Mounting type must be through-hole
Package must be compatible with TO-126-3 footprint
RoHS3 compliance and MSL 1 rating required

Substitute Categories:

Category 1: Parametric Equivalent (Identical Electrical Specifications) Parts meeting all electrical parameters of the BD434S with identical or superior ratings across all measured specifications.

Category 2: Voltage-Enhanced Substitute (Higher Voltage Rating) Parts exceeding the 22 V voltage specification while maintaining all other electrical parameters at or above BD434S levels. These substitutes provide enhanced voltage margin for applications requiring higher breakdown voltage tolerance.

Parameter Comparison

Parameter	BD434S (onsemi)	BD434S (Fairchild)	BD438G (onsemi)
Transistor Type	PNP	PNP	PNP
Current - Collector (Ic) Max	4 A	4 A	4 A
Voltage - Collector Emitter Breakdown (Max)	22 V	22 V	45 V
Vce Saturation (Max)	500 mV @ 200 mA, 2 A	500 mV @ 200 mA, 2 A	700 mV @ 300 mA, 3 A
Current - Collector Cutoff (Max)	100 µA	100 µA	100 µA
DC Current Gain (hFE) Min	40 @ 10 mA, 5 V	40 @ 10 mA, 5 V	85 @ 500 mA, 1 V
Power - Max	36 W	36 W	36 W
Frequency - Transition	3 MHz	3 MHz	3 MHz
Operating Temperature (TJ)	150°C	150°C	-55°C ~ 150°C
Mounting Type	Through Hole	Through Hole	Through Hole
Package / Case	TO-126-3	TO-126-3	TO-126-3
Product Status	Obsolete	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level	1 (Unlimited)	Not specified	1 (Unlimited)

Engineering Selection Recommendations

BD434S (Fairchild Semiconductor)

This part is a parametric equivalent to the onsemi BD434S, matching all electrical specifications and package configuration. The Fairchild variant maintains identical collector current (4 A), voltage rating (22 V), power dissipation (36 W), and transition frequency (3 MHz). Product status is active, ensuring ongoing availability. RoHS3 compliance is confirmed. This substitute is suitable for direct replacement in applications where the onsemi BD434S is specified, with no circuit modifications required.

BD438G (onsemi)

The BD438G is a voltage-enhanced substitute rated for 45 V collector-emitter breakdown, compared to the 22 V rating of the BD434S. All other electrical parameters remain equivalent: 4 A collector current, 36 W power dissipation, and 3 MHz transition frequency. The BD438G features an extended operating temperature range (-55°C to 150°C) compared to the BD434S (150°C maximum). Product status is active with confirmed RoHS3 compliance and MSL 1 rating. The BD438G is suitable for applications requiring higher voltage margin or extended low-temperature operation, provided circuit design accommodates the higher voltage rating.

Frequently Asked Questions (FAQ)

Q: Can the BD434S (Fairchild) be used as a direct replacement for the onsemi BD434S?

A: Yes. The Fairchild BD434S is a parametric equivalent with identical electrical specifications across all measured parameters: 4 A collector current, 22 V breakdown voltage, 36 W power dissipation, 3 MHz transition frequency, and 500 mV saturation voltage at specified conditions. Both devices use TO-126-3 through-hole packaging and meet RoHS3 compliance requirements. No circuit modifications are necessary.

Q: What is the primary difference between the BD434S and BD438G?

A: The BD438G features a 45 V collector-emitter breakdown voltage rating compared to the 22 V rating of the BD434S. All other electrical parameters are equivalent: 4 A maximum collector current, 36 W power dissipation, and 3 MHz transition frequency. The BD438G also provides an extended operating temperature range of -55°C to 150°C versus the BD434S maximum of 150°C.

Q: Can the BD438G replace the BD434S in any application?

A: The BD438G is electrically compatible with the BD434S for applications operating within the 22 V voltage specification. The higher 45 V rating of the BD438G provides additional voltage margin and does not degrade performance in lower-voltage applications. Both devices share identical TO-126-3 packaging and through-hole mounting. Substitution is valid provided the circuit design does not depend on the specific 22 V breakdown characteristic.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. Both the Fairchild BD434S and onsemi BD438G are confirmed ROHS3 compliant. The original onsemi BD434S is also ROHS3 compliant. All three parts meet REACH unaffected status and carry EAR99 ECCN classification.

Q: What is the moisture sensitivity level for these parts?

A: The onsemi BD434S and BD438G both carry MSL 1 (Unlimited) rating, indicating no moisture sensitivity restrictions. The Fairchild BD434S moisture sensitivity level is not specified in the provided data.

Q: Are these parts available in different packaging options?

A: All three substitute parts are specified in TO-126-3 through-hole packaging. No surface-mount or alternative package configurations are provided in the available data.

Q: Why is the onsemi BD434S classified as obsolete?

A: Product status is provided as obsolete in the component data. The Fairchild BD434S and onsemi BD438G are both active products, ensuring continued availability for new designs and production requirements.

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