MJE800G Equivalent & Substitute Parts

Part Overview

The MJE800G 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 through-hole package. This device is classified as obsolete, necessitating identification of equivalent and substitute components for ongoing design requirements and production continuity. Substitute parts maintain functional compatibility while offering alternative availability, product status, or enhanced electrical specifications.

Key Parameters

Parameter	Value
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) @ Ic, Vce	750 @ 1.5A, 3V
Vce Saturation (Max) @ Ib, Ic	2.5V @ 30mA, 1.5A
Operating Temperature Range	-55°C ~ 150°C (TJ)
Mounting Type	Through Hole
Package / Case	TO-225AA, TO-126-3

Substitute Part Grouping Explanation

Substitution eligibility for the MJE800G is determined by the following critical parameters: transistor type (NPN - Darlington), maximum collector current (4 A), maximum collector-emitter breakdown voltage (60 V minimum), maximum power dissipation (40 W), and through-hole mounting configuration. Parts are classified into two substitution categories:

Direct Substitutes maintain all critical electrical specifications and package compatibility, differing only in manufacturer, product status, or secondary parameters such as collector cutoff current or saturation voltage characteristics.

Similar Substitutes maintain core electrical specifications (4 A, 60 V, 40 W, NPN Darlington) but may exhibit variations in saturation voltage characteristics or operating temperature maximum ratings while remaining functionally compatible within the specified parameter envelope.

Parts with elevated voltage ratings (100 V) are classified as upgrades suitable for applications requiring enhanced voltage margin but remain electrically compatible due to backward compatibility of higher-rated components in lower-voltage circuits.

Parameter Comparison

Parameter	MJE800G	BD681G	KSE800STU	BD677	BD677A
Manufacturer	onsemi	onsemi	Fairchild Semiconductor	STMicroelectronics	STMicroelectronics
Product Status	Obsolete	Active	Active	Active	Active
Transistor Type	NPN - Darlington	NPN - Darlington	NPN - Darlington	NPN - Darlington	NPN - Darlington
Current - Collector (Ic) (Max)	4 A	4 A	4 A	4 A	4 A
Voltage - Collector Emitter Breakdown (Max)	60 V	100 V	60 V	60 V	60 V
Power - Max	40 W	40 W	40 W	40 W	40 W
DC Current Gain (hFE) (Min) @ Ic, Vce	750 @ 1.5A, 3V	750 @ 1.5A, 3V	750 @ 1.5A, 3V	750 @ 1.5A, 3V	750 @ 2A, 3V
Vce Saturation (Max) @ Ib, Ic	2.5V @ 30mA, 1.5A	2.5V @ 30mA, 1.5A	2.5V @ 30mA, 1.5A	2.5V @ 30mA, 1.5A	2.8V @ 40mA, 2A
Current - Collector Cutoff (Max)	100µA	500µA	100µA	500µA	500µA
Operating Temperature (TJ)	-55°C ~ 150°C	-55°C ~ 150°C	150°C	150°C	150°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Supplier Device Package	TO-126	TO-126	TO-126-3	SOT-32-3	SOT-32-3
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	Not Specified	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

BD681G is an active-status direct substitute from onsemi with identical electrical specifications to the MJE800G. The elevated collector-emitter breakdown voltage (100 V versus 60 V) provides enhanced voltage margin for applications operating near maximum ratings. This part maintains ROHS3 compliance and is suitable for direct replacement in designs where the 60 V specification is a minimum requirement. Higher inventory availability (20,300 pcs) supports production continuity.

KSE800STU is an active-status substitute from Fairchild Semiconductor with electrical specifications matching the MJE800G at the 60 V rating. The TO-126-3 package variant maintains mechanical compatibility with through-hole mounting. This part is appropriate for applications where the original 60 V specification is critical and manufacturer diversity is acceptable.

BD677 is an active-status substitute from STMicroelectronics with identical electrical specifications to the MJE800G. The SOT-32-3 package represents a mechanical variant of the through-hole form factor. Elevated collector cutoff current (500µA versus 100µA) is acceptable for applications where leakage current specifications are not restrictive. ROHS3 compliance is maintained.

BD677A is an active-status similar substitute from STMicroelectronics with core electrical specifications matching the MJE800G. Variations in saturation voltage characteristics (2.8V @ 40mA, 2A versus 2.5V @ 30mA, 1.5A) and DC current gain measurement conditions reflect device-specific performance within the Darlington family. The SOT-32-3 package maintains through-hole compatibility. ROHS3 compliance is maintained. This part is suitable for applications where saturation voltage tolerance accommodates the specified variation.

All substitute parts maintain REACH compliance and EAR99 export classification consistent with the MJE800G.

Frequently Asked Questions (FAQ)

Q: Can BD681G replace MJE800G in all applications?

A: BD681G is electrically compatible with MJE800G for applications operating at or below 60 V. The 100 V breakdown voltage rating of BD681G provides additional voltage margin and does not restrict operation in 60 V circuits. Mechanical compatibility is maintained through identical TO-126 packaging.

Q: What is the difference between TO-126 and SOT-32-3 packages?

A: Both are through-hole package variants for Darlington transistors. TO-126 and SOT-32-3 differ in physical dimensions and pin configuration. PCB layout modifications are required when substituting between these package types. Verify footprint compatibility before component selection.

Q: Are KSE800STU and MJE800G pin-compatible?

A: Both devices use TO-126-3 through-hole packaging with identical pin assignments for NPN Darlington transistors (Base, Collector, Emitter). Pin compatibility is maintained. Verify PCB footprint specifications for the specific package variant.

Q: Why does BD677A have different saturation voltage specifications?

A: BD677A saturation voltage is specified at different base and collector current conditions (40mA, 2A) compared to MJE800G (30mA, 1.5A). This reflects device characterization at different operating points within the Darlington family. Both specifications remain within acceptable saturation performance for switching applications.

Q: Which substitute part has the best availability?

A: BD681G has the highest inventory level (20,300 pcs) among active-status substitutes, supporting immediate procurement and production continuity.

Q: Are all substitute parts RoHS compliant?

A: MJE800G, BD681G, BD677, and BD677A are ROHS3 compliant. KSE800STU RoHS status is not specified in available documentation. Verify compliance requirements for your application before selection.

Q: Can I use BD681G in a circuit designed for 60 V maximum operation?

A: Yes. BD681G with 100 V breakdown voltage is suitable for circuits designed for 60 V operation. Higher voltage ratings do not restrict operation at lower voltages and provide additional safety margin.

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