BD235 Equivalent & Substitute Parts

Part Overview

The BD235 is an NPN bipolar junction transistor manufactured by STMicroelectronics, rated for 60 V collector-emitter breakdown voltage and 2 A maximum collector current. Housed in a SOT-32-3 package with through-hole mounting, this device is designed for general-purpose switching and amplification applications requiring 25 W power dissipation capability. The BD235 is classified as obsolete, necessitating identification of functionally equivalent active alternatives to maintain design continuity and ensure supply chain availability for new production and maintenance applications.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	60	V
Current - Collector (Ic) (Max)	2	A
Power - Max	25	W
Vce Saturation (Max) @ Ib, Ic	600mV @ 100mA, 1A	—
DC Current Gain (hFE) (Min) @ Ic, Vce	25 @ 1A, 2V	—
Mounting Type	Through Hole	—
Package / Case	TO-225AA, TO-126-3	—
Operating Temperature (Max)	150	°C

Substitute Part Grouping Explanation

Substitution of the BD235 is determined by strict equivalence across the following critical electrical and mechanical parameters:

Electrical Compatibility Criteria:

Transistor type must be NPN
Voltage - Collector Emitter Breakdown rating must equal or exceed 60 V
Current - Collector (Ic) maximum rating must equal or exceed 2 A
Power dissipation capability must equal or exceed 25 W
Vce saturation characteristics must be compatible at specified bias conditions
DC current gain (hFE) must support intended circuit operation

Mechanical Compatibility Criteria:

Mounting type must be Through Hole
Package must be compatible with TO-225AA or TO-126-3 footprints
Operating temperature range must support application requirements

The 2N4922G from onsemi meets the electrical requirements for voltage and saturation characteristics but operates at a reduced maximum collector current of 1 A, making it suitable only for applications where the full 2 A capability of the BD235 is not required.

Parameter Comparison

Parameter	BD235 (STMicroelectronics)	2N4922G (onsemi)	Notes
Transistor Type	NPN	NPN	Matched
Voltage - Collector Emitter Breakdown (Max)	60 V	60 V	Matched
Current - Collector (Ic) (Max)	2 A	1 A	2N4922G rated at 50% of BD235
Power - Max	25 W	30 W	2N4922G exceeds requirement
Vce Saturation (Max) @ Ib, Ic	600mV @ 100mA, 1A	600mV @ 100mA, 1A	Matched
DC Current Gain (hFE) (Min) @ Ic, Vce	25 @ 1A, 2V	30 @ 500mA, 1V	2N4922G specified at different bias point
Current - Collector Cutoff (Max)	100µA	500µA	2N4922G exhibits higher leakage
Mounting Type	Through Hole	Through Hole	Matched
Package / Case	TO-225AA, TO-126-3	TO-225AA, TO-126-3	Matched
Operating Temperature (Max)	150°C	150°C	Matched
Product Status	Obsolete	Active	2N4922G actively manufactured
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	Matched

Engineering Selection Recommendations

Primary Consideration: Product Status

The BD235 is classified as obsolete, while the 2N4922G maintains active product status with current manufacturing availability (14,100 pcs in stock versus 3,050 pcs for BD235). For new designs and long-term supply chain planning, the 2N4922G is the appropriate selection.

Electrical Suitability

The 2N4922G is electrically suitable for applications where the collector current requirement does not exceed 1 A. Both devices share identical voltage ratings (60 V), matching saturation voltage characteristics (600 mV @ 100mA, 1A), and maximum operating temperature (150°C). The 2N4922G provides superior power dissipation capability (30 W versus 25 W).

Current Rating Limitation

Applications requiring the full 2 A collector current capability of the BD235 cannot be directly substituted with the 2N4922G. In such cases, alternative NPN transistors with 2 A or greater current ratings and 60 V voltage ratings must be evaluated.

Compliance and Certification

Both devices are ROHS3 compliant, REACH unaffected, and classified under ECCN EAR99. No regulatory barriers exist to substitution.

Frequently Asked Questions (FAQ)

Q: Can the 2N4922G directly replace the BD235 in all applications?

A: The 2N4922G is suitable for applications where the maximum collector current does not exceed 1 A. If the circuit requires the full 2 A capability of the BD235, the 2N4922G is not a direct substitute. Circuit analysis must confirm that operating collector current remains below 1 A.

Q: What is the significance of the different DC current gain specifications?

A: The BD235 specifies hFE minimum of 25 @ 1A, 2V, while the 2N4922G specifies hFE minimum of 30 @ 500mA, 1V. These are measured at different bias points. The 2N4922G exhibits higher gain at lower current levels. Circuit designs relying on specific gain characteristics at 1 A and 2 V must account for this difference.

Q: Are the packages physically compatible?

A: Both devices use TO-225AA and TO-126-3 package designations, indicating physical and pin compatibility. PCB layouts designed for the BD235 will accommodate the 2N4922G without modification.

Q: Why does the 2N4922G have higher collector cutoff current?

A: The 2N4922G specifies ICBO (collector cutoff current) at 500µA maximum, compared to 100µA for the BD235. This represents higher leakage current in the off state. For applications sensitive to leakage current, this difference must be evaluated against circuit requirements.

Q: What is the operating temperature range for the 2N4922G?

A: The 2N4922G operates from −65°C to 150°C, providing a wider low-temperature range than the BD235 specification of 150°C maximum. This extended range supports applications requiring operation at sub-zero temperatures.

Q: Is the 2N4922G available in the same packaging as the BD235?

A: Yes. The 2N4922G is supplied in TO-126 package format, which corresponds to the TO-126-3 designation used for the BD235. Both devices are through-hole mounted components with identical pin configurations.

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