MMBT6428 NPN Bipolar Junction Transistor Equivalent & Substitute Parts

Part Overview

The MMBT6428 is an NPN bipolar junction transistor manufactured by onsemi, designed for surface mount applications in the SOT-23-3 package. This device operates at a maximum collector current of 500 mA with a 50 V collector-emitter breakdown voltage and 700 MHz transition frequency. The MMBT6428 is classified as obsolete, necessitating identification of active equivalent and substitute components for new designs and ongoing production requirements. Substitute parts must maintain functional compatibility while meeting current manufacturing and compliance standards.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Collector Current (Ic) Maximum	500	mA
Collector-Emitter Breakdown Voltage (Vceo)	50	V
Power Dissipation Maximum	350	mW
Transition Frequency (fT)	700	MHz
Operating Temperature Range	−55 to +150	°C
Package Type	SOT-23-3 (TO-236-3, SC-59)	—
Mounting Type	Surface Mount	—

Substitute Part Grouping Explanation

Substitution of the MMBT6428 is determined by strict adherence to the following electrical and mechanical parameters:

Primary Substitution Criteria:

Transistor type must be NPN
Collector-emitter breakdown voltage (Vceo) must be greater than or equal to 50 V
Collector current rating (Ic) must be greater than or equal to 500 mA
Power dissipation must be greater than or equal to 350 mW
Transition frequency must be greater than or equal to 700 MHz
Package must be SOT-23-3 (TO-236-3, SC-59) surface mount
Operating temperature range must encompass −55°C to +150°C

Direct Equivalent Classification: Parts meeting all primary criteria with identical or superior electrical performance are classified as direct equivalents.

Similar Substitute Classification: Parts that meet the core electrical requirements but have reduced performance in one or more parameters (lower Vceo, lower fT, lower power dissipation, or lower Ic) are classified as similar substitutes. These parts are suitable only when the application does not require the full performance envelope of the original MMBT6428.

Parameter Comparison

Part Number	Manufacturer	Product Status	Ic (Max) mA	Vceo (Max) V	Power (Max) mW	fT MHz	Temp Range °C	Package	RoHS Status
MMBT6428	onsemi	Obsolete	500	50	350	700	−55 to +150	SOT-23-3	—
MMBT6428LT1G	onsemi	Active	200	50	225	700	−55 to +150	SOT-23-3	ROHS3 Compliant
50C02CH-TL-E	onsemi	Active	500	50	700	500	−55 to +150	SOT-23-3	ROHS3 Compliant
BC817-16LT1G	onsemi	Active	500	45	300	100	−65 to +150	SOT-23-3	ROHS3 Compliant
BC817-16LT3G	onsemi	Active	500	45	300	100	−65 to +150	SOT-23-3	ROHS3 Compliant
BC817-25LT1G	onsemi	Active	500	45	300	100	−65 to +150	SOT-23-3	ROHS3 Compliant
BC817-25LT3G	onsemi	Active	500	45	300	100	−65 to +150	SOT-23-3	ROHS3 Compliant
BC817-40LT1G	onsemi	Active	500	45	300	100	−65 to +150	SOT-23-3	ROHS3 Compliant
BC817-40LT3G	onsemi	Active	500	45	300	100	−65 to +150	SOT-23-3	ROHS3 Compliant
BCX19LT1G	onsemi	Active	500	45	300	—	−55 to +150	SOT-23-3	ROHS3 Compliant
MMBT6429LT1G	onsemi	Active	200	45	225	700	−55 to +150	SOT-23-3	ROHS3 Compliant

Engineering Selection Recommendations

Direct Equivalent (Recommended for Direct Replacement):

The MMBT6428 has no direct equivalent among the provided substitute parts. No single part meets all electrical specifications (500 mA Ic, 50 V Vceo, 350 mW power, 700 MHz fT) while maintaining active product status.

Primary Substitute Selection:

50C02CH-TL-E is the closest functional substitute. This part maintains the 500 mA collector current and 50 V breakdown voltage specifications of the original MMBT6428. The 50C02CH-TL-E exceeds the power dissipation requirement at 700 mW and operates within the required temperature range. The transition frequency is reduced to 500 MHz, which represents a performance reduction in high-frequency applications. This part is ROHS3 compliant and carries active product status.

Secondary Substitute Selection:

MMBT6428LT1G is an active onsemi part with identical voltage and frequency specifications to the original MMBT6428. However, the collector current is limited to 200 mA and power dissipation to 225 mW. This part is suitable only for applications where the circuit current requirements do not exceed 200 mA.

Alternative Substitutes for Lower-Performance Applications:

The BC817 series (BC817-16LT1G, BC817-16LT3G, BC817-25LT1G, BC817-25LT3G, BC817-40LT1G, BC817-40LT3G) and BCX19LT1G are suitable substitutes for applications that do not require the full 50 V breakdown voltage or 700 MHz transition frequency. These parts operate at 45 V maximum breakdown voltage and 100 MHz transition frequency (except BCX19LT1G, which does not specify fT). All maintain 500 mA collector current capability and are ROHS3 compliant with active product status.

MMBT6429LT1G combines reduced current (200 mA) and voltage (45 V) specifications but maintains the 700 MHz transition frequency. This part is suitable for low-current, high-frequency applications.

All recommended substitutes are manufactured by onsemi, carry ROHS3 compliance certification, and maintain the SOT-23-3 surface mount package format.

Frequently Asked Questions (FAQ)

Q: Can MMBT6428LT1G be used as a direct replacement for MMBT6428?

A: MMBT6428LT1G is not a direct replacement. While it maintains identical voltage (50 V) and frequency (700 MHz) specifications, the collector current is reduced from 500 mA to 200 mA and power dissipation from 350 mW to 225 mW. Use this part only if your circuit operates at collector currents below 200 mA.

Q: What is the primary limitation of BC817 series substitutes?

A: The BC817 series (all variants) operates at a maximum breakdown voltage of 45 V compared to the MMBT6428 specification of 50 V. Additionally, transition frequency is reduced to 100 MHz from 700 MHz. These parts are suitable for applications not requiring the full voltage or frequency performance of the original device.

Q: Is 50C02CH-TL-E a suitable substitute for high-frequency applications?

A: The 50C02CH-TL-E maintains the 500 mA current and 50 V voltage specifications of the MMBT6428 but operates at 500 MHz transition frequency compared to the original 700 MHz. For applications requiring operation above 500 MHz, this part does not meet the frequency requirement.

Q: Are all substitute parts ROHS3 compliant?

A: All substitute parts listed carry ROHS3 compliance certification. The original MMBT6428 does not specify RoHS status. All active substitutes meet current environmental compliance standards.

Q: What is the difference between packaging variants (LT1G vs. LT3G)?

A: The packaging designation indicates different tape and reel configurations. LT1G and LT3G variants are functionally identical in electrical performance. Selection between these variants depends on procurement and assembly requirements.

Q: Can BCX19LT1G be used in applications requiring 700 MHz operation?

A: No. The BCX19LT1G does not specify a transition frequency parameter. This part is not suitable for applications requiring guaranteed 700 MHz operation.

Q: What is the minimum collector current at which MMBT6428LT1G operates reliably?

A: The provided specifications indicate DC current gain (hFE) minimum of 250 at 100 µA collector current and 5 V Vce. Operation below this current level is not specified in the provided parameters.

Q: Are there any temperature range differences between substitutes?

A: The BC817 series operates from −65°C to +150°C, providing a lower temperature limit 10°C below the MMBT6428 specification of −55°C to +150°C. All other substitutes maintain the −55°C to +150°C range. For applications requiring operation below −55°C, BC817 variants provide extended low-temperature capability.

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