STN878 Equivalent & Substitute Parts

Part Overview

The STN878 is an NPN bipolar junction transistor manufactured by STMicroelectronics, designed for surface mount applications in the SOT-223 package. This component is rated for 30 V collector-emitter breakdown voltage and 5 A maximum collector current with 1.6 W power dissipation capability. The STN878 is classified as obsolete, necessitating identification of active equivalent and substitute components for ongoing design requirements and production continuity.

Key Parameters

Parameter	Value
Transistor Type	NPN
Current - Collector (Ic) (Max)	5 A
Voltage - Collector Emitter Breakdown (Max)	30 V
Power - Max	1.6 W
Vce Saturation (Max) @ Ib, Ic	1.2 V @ 500 mA, 10 A
DC Current Gain (hFE) (Min) @ Ic, Vce	100 @ 500 mA, 1 V
Package / Case	SOT-223
Mounting Type	Surface Mount
Operating Temperature (Max)	150°C
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution of the STN878 is determined by electrical and mechanical compatibility across the following critical parameters:

Primary Substitution Criteria:

Transistor Type: NPN configuration required
Collector Current Rating: Minimum 5 A capability
Collector-Emitter Breakdown Voltage: Minimum 30 V rating
Package Type: SOT-223 surface mount configuration
Power Dissipation: Minimum 1.6 W capability
Operating Temperature Range: Support for 150°C maximum junction temperature

Substitution Logic: Parts are classified as direct substitutes when they meet or exceed the STN878 electrical specifications while maintaining identical or compatible package geometry. Enhanced specifications (higher voltage ratings, increased current capacity, or improved power handling) do not preclude substitution provided the part operates within the same thermal and mechanical envelope.

The FZT1051ATA and FZT1051ATC variants from Diodes Incorporated exceed the STN878 specifications with 40 V breakdown voltage and 2.5 W power rating while maintaining 5 A collector current and SOT-223 packaging. The FZT849TA provides equivalent 30 V breakdown voltage with enhanced 7 A collector current capability and 3 W power dissipation, also in SOT-223 packaging.

Parameter Comparison

Parameter	STN878	FZT1051ATA	FZT1051ATC	FZT849TA
Manufacturer	STMicroelectronics	Diodes Incorporated	Diodes Incorporated	Diodes Incorporated
Product Status	Obsolete	Active	Active	Active
Transistor Type	NPN	NPN	NPN	NPN
Current - Collector (Ic) (Max)	5 A	5 A	5 A	7 A
Voltage - Collector Emitter Breakdown (Max)	30 V	40 V	40 V	30 V
Vce Saturation (Max) @ Ib, Ic	1.2 V @ 500 mA, 10 A	340 mV @ 100 mA, 5 A	340 mV @ 100 mA, 5 A	350 mV @ 300 mA, 6.5 A
DC Current Gain (hFE) (Min) @ Ic, Vce	100 @ 500 mA, 1 V	270 @ 1 A, 2 V	270 @ 1 A, 2 V	100 @ 1 A, 1 V
Power - Max	1.6 W	2.5 W	2.5 W	3 W
Frequency - Transition	Not specified	155 MHz	155 MHz	100 MHz
Operating Temperature (TJ)	150°C (Max)	-55°C ~ 150°C	-55°C ~ 150°C	-55°C ~ 150°C
Package / Case	SOT-223	SOT-223-3	SOT-223-3	SOT-223-3
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)
REACH Status	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected

Engineering Selection Recommendations

FZT1051ATA and FZT1051ATC Selection: Both FZT1051 variants are active products from Diodes Incorporated with full ROHS3 compliance and REACH unaffected status. These parts provide enhanced electrical performance with 40 V breakdown voltage and 2.5 W power dissipation, exceeding STN878 specifications. The primary distinction between FZT1051ATA and FZT1051ATC is packaging format: FZT1051ATA is supplied in Cut Tape (CT) configuration with 15,325 units in stock, while FZT1051ATC is supplied in Tape & Reel (TR) configuration with 20,300 units in stock. Selection between these variants depends on procurement and assembly requirements rather than electrical performance.

FZT849TA Selection: The FZT849TA is an active product from Diodes Incorporated offering equivalent 30 V breakdown voltage to the STN878 with enhanced 7 A collector current capability and 3 W power dissipation. This part maintains full ROHS3 compliance and REACH unaffected status. The FZT849TA is available in Tape & Reel (TR) packaging with 35,200 units in stock. This variant is suitable for applications requiring higher current capacity within the same voltage envelope.

All substitute parts maintain SOT-223 surface mount packaging compatibility, unlimited moisture sensitivity level (MSL 1), and operating temperature support to 150°C junction temperature, ensuring direct mechanical and thermal compatibility with existing PCB designs.

Frequently Asked Questions (FAQ)

Q: Can FZT1051ATA or FZT1051ATC be used as direct replacements for STN878?

A: Yes. Both FZT1051 variants meet or exceed all critical electrical parameters of the STN878. The 40 V breakdown voltage rating provides additional design margin compared to the STN878 30 V specification. Both parts are packaged in SOT-223-3 configuration, compatible with existing STN878 PCB footprints. The primary selection criterion between FZT1051ATA and FZT1051ATC is packaging format: Cut Tape for lower volume requirements or Tape & Reel for higher volume production.

Q: What is the difference between FZT1051ATA and FZT1051ATC?

A: FZT1051ATA and FZT1051ATC are electrically identical NPN transistors with identical electrical specifications. The difference is packaging format only. FZT1051ATA is supplied in Cut Tape (CT) configuration, while FZT1051ATC is supplied in Tape & Reel (TR) configuration. Selection depends on assembly equipment compatibility and procurement volume requirements.

Q: When should FZT849TA be selected instead of FZT1051 variants?

A: FZT849TA is selected when the application requires collector current capability exceeding 5 A. The FZT849TA is rated for 7 A maximum collector current with 3 W power dissipation, compared to 5 A and 2.5 W for FZT1051 variants. Both maintain 30 V breakdown voltage matching the STN878 specification. FZT849TA is suitable for higher current switching applications within the same voltage class.

Q: Are all substitute parts compatible with existing STN878 PCB designs?

A: Yes. All substitute parts (FZT1051ATA, FZT1051ATC, and FZT849TA) are packaged in SOT-223-3 configuration, which is mechanically compatible with STN878 SOT-223 footprints. Pin configuration and lead spacing are identical, allowing direct PCB substitution without layout modifications.

Q: What compliance certifications apply to substitute parts?

A: All substitute parts are ROHS3 compliant and REACH unaffected. Moisture sensitivity level is MSL 1 (unlimited) for all parts, matching the STN878 specification. ECCN classification is EAR99 for all parts.

Q: Why is the STN878 classified as obsolete?

A: The STN878 is an obsolete product from STMicroelectronics. Active equivalent products from Diodes Incorporated (FZT1051 and FZT849 series) provide equivalent or enhanced functionality with ongoing manufacturing support and availability.

Q: Can substitute parts operate at the same temperature range as STN878?

A: Yes. All substitute parts support maximum junction temperature of 150°C, matching the STN878 specification. FZT1051 and FZT849 variants additionally specify minimum operating temperature of -55°C, providing extended low-temperature capability compared to the STN878 specification which lists only maximum temperature.

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