BD138 Equivalent & Substitute Parts

Part Overview

The BD138 is a PNP bipolar junction transistor (BJT) rated for 60 V collector-emitter breakdown voltage and 1.5 A maximum collector current in a Through Hole TO-126 package. The original onsemi BD138 carries an Obsolete product status, necessitating identification of equivalent and substitute components for ongoing design support and procurement.

Key Parameters

Parameter	Value
Transistor Type	PNP
Current - Collector (Ic) (Max)	1.5 A
Voltage - Collector Emitter Breakdown (Max)	60 V
Vce Saturation (Max) @ Ib, Ic	500mV @ 50mA, 500mA
Current - Collector Cutoff (Max)	100nA (ICBO)
DC Current Gain (hFE) (Min) @ Ic, Vce	40 @ 150mA, 2V
Power - Max	1.25 W
Operating Temperature	-55°C ~ 150°C (TJ)
Mounting Type	Through Hole
Package / Case	TO-225AA, TO-126-3

Substitute Part Grouping Explanation

Substitution of the BD138 is determined by electrical and mechanical parameter equivalence. The critical parameters governing substitutability are:

Transistor polarity (PNP)
Maximum collector current (1.5 A)
Maximum collector-emitter breakdown voltage (60 V)
Saturation voltage characteristics (500mV @ 50mA, 500mA)
Collector cutoff current (100nA ICBO)
Maximum power dissipation (1.25 W)
Through Hole mounting configuration
Compatible package footprints (TO-126-3 or equivalent)

Parts meeting all these electrical specifications and physical mounting requirements are classified as direct equivalents or substitutes. Variations in DC current gain (hFE), product status, compliance certifications, and packaging format (Bulk, Tube) do not affect functional substitutability within the specified electrical operating range.

Parameter Comparison

Parameter	BD138 (onsemi)	BD138G (onsemi)	BD13810STU (Fairchild)	BD138 (STMicroelectronics)
Transistor Type	PNP	PNP	PNP	PNP
Current - Collector (Ic) (Max)	1.5 A	1.5 A	1.5 A	1.5 A
Voltage - Collector Emitter Breakdown (Max)	60 V	60 V	60 V	60 V
Vce Saturation (Max) @ Ib, Ic	500mV @ 50mA, 500mA	500mV @ 50mA, 500mA	500mV @ 50mA, 500mA	500mV @ 50mA, 500mA
Current - Collector Cutoff (Max)	100nA (ICBO)	100nA (ICBO)	100nA (ICBO)	100nA (ICBO)
DC Current Gain (hFE) (Min) @ Ic, Vce	40 @ 150mA, 2V	40 @ 150mA, 2V	63 @ 150mA, 2V	40 @ 150mA, 2V
Power - Max	1.25 W	1.25 W	1.25 W	1.25 W
Operating Temperature	-55°C ~ 150°C (TJ)	-55°C ~ 150°C (TJ)	150°C (TJ)	150°C (TJ)
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	TO-225AA, TO-126-3	TO-225AA, TO-126-3	TO-225AA, TO-126-3	TO-225AA, TO-126-3
Product Status	Obsolete	Active	Active	Active
RoHS Status	Non-compliant	ROHS3 Compliant	Not specified	ROHS3 Compliant

Engineering Selection Recommendations

BD138G (onsemi) is the direct equivalent replacement for the obsolete BD138. This part maintains identical electrical specifications and operating temperature range while carrying Active product status and ROHS3 compliance certification. The BD138G is suitable for all applications previously using the original BD138.

BD13810STU (Fairchild Semiconductor) is a functional substitute meeting all core electrical parameters. This part exhibits higher DC current gain (63 vs. 40 @ 150mA, 2V), which may provide improved switching characteristics in applications sensitive to base drive requirements. The operating temperature maximum is specified at 150°C without the lower -55°C limit. This part is appropriate for applications operating within the 0°C to 150°C range.

BD138 (STMicroelectronics) is a functional substitute with identical electrical specifications to the original onsemi part. This variant is supplied in SOT-32-3 package format (Tube packaging) rather than TO-126, requiring PCB footprint verification before selection. ROHS3 compliance and Active product status support long-term availability.

Selection between active substitutes depends on package availability, supply chain requirements, and thermal operating range specifications of the target application.

Frequently Asked Questions (FAQ)

Q: Can BD138G directly replace the obsolete onsemi BD138 without circuit modification?

A: Yes. The BD138G maintains identical electrical specifications, saturation voltage characteristics, current ratings, and operating temperature range. No circuit modifications are required.

Q: What is the difference between BD138G and BD13810STU?

A: Both parts meet the core electrical specifications (1.5 A, 60 V, 1.25 W). The BD13810STU exhibits higher DC current gain (63 vs. 40 @ 150mA, 2V) and specifies a maximum operating temperature of 150°C without the lower -55°C limit. The BD138G supports the full -55°C to 150°C range.

Q: Are all substitute parts compatible with TO-126 PCB footprints?

A: The BD138G and BD13810STU are compatible with TO-126-3 footprints. The STMicroelectronics BD138 uses SOT-32-3 package format, which requires verification of PCB footprint compatibility before selection.

Q: Does the higher DC current gain of BD13810STU affect circuit operation?

A: Higher DC current gain (hFE) reduces base drive requirements for saturation. In applications designed for the nominal 40 hFE specification, the BD13810STU will saturate with lower base current. Circuit operation remains functional; base resistor values may require adjustment for optimized switching performance.

Q: What compliance certifications apply to substitute parts?

A: BD138G and STMicroelectronics BD138 carry ROHS3 compliance certification. All parts are REACH Unaffected and classified as EAR99 for export control purposes.

Q: Is moisture sensitivity a consideration for these parts?

A: The onsemi BD138 and BD138G specify Moisture Sensitivity Level 1 (Unlimited), indicating no moisture sensitivity precautions are required. Standard handling and storage practices apply.

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