BC373G Equivalent & Substitute Parts

Part Overview

The BC373G is an NPN Darlington bipolar junction transistor manufactured by onsemi, designed for general-purpose switching and amplification applications. This device features an 80 V collector-emitter breakdown voltage rating and a maximum collector current of 1 A, housed in a TO-92 through-hole package. The BC373G is classified as obsolete, making identification of functionally equivalent alternatives necessary for ongoing design support and procurement continuity.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN - Darlington	—
Current - Collector (Ic) (Max)	1	A
Voltage - Collector Emitter Breakdown (Max)	80	V
Power - Max	625	mW
Frequency - Transition	200	MHz
Operating Temperature Range	-55 to 150	°C
Mounting Type	Through Hole	—
Package / Case	TO-92-3	—

Substitute Part Grouping Explanation

Substitution of the BC373G is determined by equivalence across the following critical parameters:

Transistor Configuration: NPN Darlington topology
Maximum Collector Current: 1 A minimum rating
Collector-Emitter Breakdown Voltage: 80 V minimum rating
Package Compatibility: TO-92 or TO-92-compatible form factor for through-hole mounting
Operating Temperature Range: Minimum coverage of -55°C to 150°C

The ZTX603 manufactured by Diodes Incorporated satisfies all substitution criteria. Both devices operate as NPN Darlington transistors with identical maximum collector current (1 A) and collector-emitter breakdown voltage (80 V) ratings. The ZTX603 is housed in an E-Line package, which is mechanically and electrically compatible with TO-92 through-hole mounting. The ZTX603 extends the upper operating temperature limit to 200°C, providing enhanced thermal performance beyond the BC373G specification.

Parameter Comparison

Parameter	BC373G (onsemi)	ZTX603 (Diodes Incorporated)	Unit
Transistor Type	NPN - Darlington	NPN - Darlington	—
Current - Collector (Ic) (Max)	1	1	A
Voltage - Collector Emitter Breakdown (Max)	80	80	V
Vce Saturation (Max)	1.1 @ 250µA, 250mA	1.0 @ 1mA, 1A	V
DC Current Gain (hFE) (Min)	10000 @ 100mA, 5V	2000 @ 1A, 5V	—
Power - Max	625	1000	mW
Frequency - Transition	200	150	MHz
Operating Temperature Range	-55 to 150	-55 to 200	°C
Mounting Type	Through Hole	Through Hole	—
Package / Case	TO-92-3	E-Line-3 (TO-92 compatible)	—

Engineering Selection Recommendations

The BC373G is classified as obsolete, necessitating transition to active alternatives for new designs and ongoing procurement. The ZTX603 is the qualified substitute, carrying active product status from Diodes Incorporated.

Compliance and Certification Status:

BC373G: REACH Unaffected; ECCN EAR99; Moisture Sensitivity Level 1 (Unlimited)
ZTX603: RoHS3 Compliant; REACH Unaffected; ECCN EAR99; Moisture Sensitivity Level 1 (Unlimited)

The ZTX603 provides enhanced regulatory compliance through RoHS3 certification, supporting modern procurement and environmental standards. Both devices are classified under ECCN EAR99 and carry unlimited moisture sensitivity ratings, indicating no special handling requirements.

The ZTX603 offers superior power dissipation capability (1 W versus 625 mW) and extended operating temperature range (-55°C to 200°C versus -55°C to 150°C), providing design margin for thermal and power management considerations. The transition frequency of the ZTX603 (150 MHz) remains suitable for general-purpose switching applications within the BC373G's intended operating envelope.

Frequently Asked Questions (FAQ)

Q: Can the ZTX603 directly replace the BC373G in existing designs?

A: Yes. Both devices are NPN Darlington transistors with identical maximum collector current (1 A) and collector-emitter breakdown voltage (80 V) ratings. The ZTX603 E-Line package is mechanically and electrically compatible with TO-92 through-hole mounting. Pin configuration and functional behavior are equivalent for standard switching and amplification applications.

Q: What are the key differences between BC373G and ZTX603?

A: The ZTX603 provides higher maximum power dissipation (1 W versus 625 mW), extended operating temperature range (200°C upper limit versus 150°C), and RoHS3 compliance. The BC373G exhibits higher transition frequency (200 MHz versus 150 MHz) and higher DC current gain at specified test conditions. These differences do not prevent substitution in applications designed within BC373G specifications.

Q: Are there package compatibility concerns when substituting BC373G with ZTX603?

A: No. The ZTX603 E-Line package is specified as TO-92 compatible and maintains identical through-hole mounting characteristics. Both devices use three-lead configurations suitable for standard PCB footprints designed for TO-92 packages.

Q: What is the product status difference between these devices?

A: The BC373G is classified as obsolete, indicating discontinued manufacturing and limited availability. The ZTX603 is active, ensuring ongoing availability and manufacturing support from Diodes Incorporated.

Q: Does the ZTX603 meet modern regulatory requirements?

A: Yes. The ZTX603 is RoHS3 compliant and REACH unaffected, meeting current environmental and regulatory standards. The BC373G is REACH unaffected but does not carry RoHS certification due to its obsolete status.

Q: Are there thermal performance considerations for substitution?

A: The ZTX603 supports higher maximum junction temperature (200°C versus 150°C) and higher power dissipation (1 W versus 625 mW). Applications operating near the BC373G thermal limits benefit from the ZTX603's enhanced thermal capability. No derating adjustments are required for designs operating within BC373G specifications.

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