BD235-BP Equivalent & Substitute Parts

Part Overview

The BD235-BP is an NPN bipolar junction transistor manufactured by Micro Commercial Co, rated for 60V collector-emitter breakdown voltage and 2A maximum collector current in a TO-126 through-hole package. This component is classified as obsolete, making identification of functionally equivalent alternatives necessary for ongoing design support and production continuity. The BD235-BP delivers 1.25W maximum power dissipation with a 3MHz transition frequency, suitable for general-purpose switching and amplification applications in legacy systems.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	60	V
Current - Collector (Ic) (Max)	2	A
Power - Max	1.25	W
DC Current Gain (hFE) (Min) @ Ic, Vce	40 @ 150mA, 2V	—
Vce Saturation (Max)	600mV @ 100mA, 1A	—
Mounting Type	Through Hole	—
Package / Case	TO-126-3	—
Operating Temperature (Max)	150	°C

Substitute Part Grouping Explanation

Substitution of the BD235-BP is determined by equivalence across the following critical parameters:

Mandatory Matching Criteria:

Transistor polarity: NPN
Collector-emitter breakdown voltage: 60V minimum
Package type: TO-126 through-hole configuration
RoHS3 compliance status
Operating temperature range compatibility

Allowable Parameter Variance:

Maximum collector current may be equal to or greater than the original 2A specification
Maximum power dissipation must be equal to or greater than 1.25W
DC current gain (hFE) must meet or exceed 40 @ 150mA, 2V
Vce saturation characteristics must support the application's switching requirements

The BD137G qualifies as a direct substitute based on matching voltage rating (60V), identical package (TO-126), equivalent power rating (1.25W), matching DC current gain specification (40 @ 150mA, 2V), and active product status with current manufacturing availability.

Parameter Comparison

Parameter	BD235-BP	BD137G	Unit
Manufacturer	Micro Commercial Co	onsemi	—
Transistor Type	NPN	NPN	—
Voltage - Collector Emitter Breakdown (Max)	60	60	V
Current - Collector (Ic) (Max)	2	1.5	A
Power - Max	1.25	1.25	W
DC Current Gain (hFE) (Min) @ Ic, Vce	40 @ 150mA, 2V	40 @ 150mA, 2V	—
Vce Saturation (Max)	600mV @ 100mA, 1A	500mV @ 50mA, 500mA	—
Package / Case	TO-126-3	TO-126-3	—
Mounting Type	Through Hole	Through Hole	—
Operating Temperature (Max)	150	150	°C
Product Status	Obsolete	Active	—
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	—

Engineering Selection Recommendations

The BD137G is a qualified substitute for the BD235-BP based on the following engineering criteria:

Voltage and Package Compatibility: Both devices share identical 60V collector-emitter breakdown voltage ratings and TO-126 through-hole packaging, ensuring direct mechanical and electrical compatibility in existing PCB layouts without modification.

Current Rating Consideration: The BD137G maximum collector current is rated at 1.5A compared to the BD235-BP's 2A specification. Applications requiring sustained collector currents above 1.5A must be evaluated against actual circuit operating conditions. The BD137G remains suitable for applications operating at or below 1.5A.

Power Dissipation: Both devices are rated for 1.25W maximum power dissipation, providing equivalent thermal performance in standard TO-126 mounting configurations.

Gain and Saturation Characteristics: The DC current gain specification (40 @ 150mA, 2V) is identical between both devices. The BD137G exhibits lower Vce saturation voltage (500mV @ 50mA, 500mA) compared to the BD235-BP (600mV @ 100mA, 1A), representing improved switching efficiency.

Compliance and Availability: The BD137G holds active product status with ROHS3 compliance certification, ensuring long-term supply availability and regulatory alignment. The BD235-BP's obsolete status necessitates transition to the BD137G for new production and ongoing support.

Frequently Asked Questions (FAQ)

Q: Can the BD137G directly replace the BD235-BP in existing designs?

A: The BD137G is a direct mechanical and electrical substitute for applications operating at collector currents of 1.5A or below. Both devices share identical 60V voltage ratings, TO-126 packaging, 1.25W power ratings, and DC current gain specifications. No PCB modifications are required. Applications requiring sustained currents above 1.5A must be reassessed.

Q: What is the primary difference between these two transistors?

A: The BD235-BP is rated for 2A maximum collector current, while the BD137G is rated for 1.5A. The BD137G exhibits superior Vce saturation characteristics (500mV versus 600mV), resulting in lower power dissipation during saturation. The BD137G is an active product with current manufacturing support, whereas the BD235-BP is obsolete.

Q: Are there any thermal or mounting differences?

A: Both transistors use identical TO-126 through-hole packaging and are rated for 150°C maximum junction temperature. Thermal performance is equivalent when mounted in standard configurations. No changes to heatsinking or PCB layout are necessary.

Q: Does the lower current rating of the BD137G affect circuit performance?

A: The BD137G's 1.5A rating is sufficient for applications designed within this specification. If the original design requires sustained collector currents exceeding 1.5A, the circuit must be evaluated to determine if operation can be maintained at or below 1.5A, or if alternative components with higher current ratings are necessary.

Q: Are both devices RoHS compliant?

A: Yes, both the BD235-BP and BD137G are ROHS3 compliant, meeting current environmental and regulatory requirements for electronic component manufacturing and use.

Q: Why is the BD235-BP listed as obsolete?

A: The BD235-BP has been discontinued by its manufacturer. The BD137G represents the active equivalent in the market, providing equivalent functionality with improved specifications and ongoing manufacturing support.

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