MJE800STU Equivalent & Substitute Parts

Part Overview

The MJE800STU is an NPN Darlington bipolar junction transistor manufactured by onsemi, rated for 60 V collector-emitter breakdown voltage and 4 A maximum collector current in a TO-126-3 through-hole package. This device is classified as obsolete, necessitating identification of active equivalent and substitute components for ongoing design support and procurement continuity.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN - Darlington	—
Current - Collector (Ic) (Max)	4	A
Voltage - Collector Emitter Breakdown (Max)	60	V
Power - Max	40	W
DC Current Gain (hFE) (Min)	750	—
Operating Temperature (TJ)	150	°C
Mounting Type	Through Hole	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the MJE800STU is determined by equivalence in the following electrical and mechanical parameters: NPN Darlington transistor topology, 60 V maximum collector-emitter breakdown voltage, 4 A maximum collector current, 40 W maximum power dissipation, 750 minimum DC current gain, 150°C maximum junction temperature, and through-hole mounting configuration.

The substitute parts identified—KSE800STU, BD677, and BD677A—satisfy these core requirements. Variations in saturation voltage characteristics and collector cutoff current do not preclude substitution when the primary electrical ratings and functional topology remain equivalent. Package designations (TO-126-3 and SOT-32-3) are both through-hole configurations compatible with standard PCB layouts for this device class.

Parameter Comparison

Parameter	MJE800STU (onsemi)	KSE800STU (Fairchild)	BD677 (STMicroelectronics)	BD677A (STMicroelectronics)
Transistor Type	NPN - Darlington	NPN - Darlington	NPN - Darlington	NPN - Darlington
Current - Collector (Ic) (Max)	4 A	4 A	4 A	4 A
Voltage - Collector Emitter Breakdown (Max)	60 V	60 V	60 V	60 V
Vce Saturation (Max) @ Ib, Ic	2.5V @ 30mA, 1.5A	2.5V @ 30mA, 1.5A	2.5V @ 30mA, 1.5A	2.8V @ 40mA, 2A
Current - Collector Cutoff (Max)	100µA	100µA	500µA	500µA
DC Current Gain (hFE) (Min) @ Ic, Vce	750 @ 1.5A, 3V	750 @ 1.5A, 3V	750 @ 1.5A, 3V	750 @ 2A, 3V
Power - Max	40 W	40 W	40 W	40 W
Operating Temperature (TJ)	150°C	150°C	150°C	150°C
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
Supplier Device Package	TO-126-3	TO-126-3	SOT-32-3	SOT-32-3
Product Status	Obsolete	Active	Active	Active
RoHS Status	ROHS3 Compliant	Not specified	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

KSE800STU (Fairchild Semiconductor) provides direct electrical and package equivalence to the MJE800STU. This part maintains identical saturation voltage and current gain specifications at the same test conditions. The TO-126-3 package matches the original device footprint. Product status is active, ensuring procurement availability.

BD677 (STMicroelectronics) offers electrical equivalence with identical core ratings (60 V, 4 A, 40 W, 750 hFE minimum). The SOT-32-3 package is a through-hole configuration compatible with standard PCB layouts. Collector cutoff current is specified at 500µA versus 100µA for the MJE800STU; this parameter difference does not affect functional substitution in typical switching and amplification applications. Product status is active with ROHS3 compliance confirmed.

BD677A (STMicroelectronics) is a variant of the BD677 with modified saturation voltage and current gain test conditions (2.8V @ 40mA, 2A and 750 @ 2A, 3V respectively). This part maintains the same maximum ratings and operating temperature. The SOT-32-3 package provides through-hole compatibility. Product status is active with ROHS3 compliance confirmed.

All substitute parts are REACH Unaffected and classified under ECCN EAR99 where specified, maintaining regulatory alignment with the original device.

Frequently Asked Questions (FAQ)

Q: Can KSE800STU replace MJE800STU in existing designs without PCB modification?

A: Yes. The KSE800STU is electrically equivalent and supplied in the TO-126-3 package, matching the MJE800STU footprint. No PCB layout changes are required.

Q: What is the difference between BD677 and BD677A?

A: Both devices meet the 60 V, 4 A, 40 W ratings and 750 minimum hFE specification. BD677A specifies saturation voltage at higher base and collector currents (40mA, 2A versus 30mA, 1.5A). Selection between these variants depends on the specific bias point of the application circuit.

Q: Are BD677 and BD677A compatible with TO-126-3 PCB layouts?

A: BD677 and BD677A are supplied in SOT-32-3 packages, which are through-hole configurations. Pin assignments and lead spacing differ from TO-126-3. PCB layout verification is required before substitution. Both packages are through-hole mount types suitable for standard component insertion.

Q: Does the higher collector cutoff current (500µA) of BD677 and BD677A affect circuit performance?

A: Collector cutoff current (Icbo) is a leakage parameter measured with the base open-circuited. In typical switching and linear amplification circuits, this parameter has negligible impact on circuit operation. Applications with extremely high impedance base circuits or precision analog designs should evaluate this specification against circuit requirements.

Q: Are all substitute parts RoHS compliant?

A: MJE800STU, BD677, and BD677A are confirmed ROHS3 compliant. KSE800STU RoHS status is not specified in available documentation. Compliance verification with the KSE800STU manufacturer is recommended for applications with RoHS requirements.

Q: What is the inventory status of these substitute parts?

A: KSE800STU: 1798 pcs in stock. BD677: 1804 pcs in stock. BD677A: 2443 pcs in stock. All substitute parts are available as new original components.

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