START405TR RF Transistor NPN Equivalent & Substitute Parts

Part Overview

The START405TR is an RF transistor NPN manufactured by STMicroelectronics, designed for surface mount applications in the SC-82A SOT-343 package. This device operates at 4.5V collector-emitter breakdown voltage with a maximum power dissipation of 45mW and supports collector currents up to 10mA. The part is classified as obsolete, making identification of suitable substitute components necessary for ongoing design support and production continuity. Equivalent parts must maintain compatibility with the SOT-343 package footprint and support RF applications within the specified voltage and current parameters.

Key Parameters

Parameter	Value	Unit
Manufacturer Part Number	START405TR	—
Manufacturer	STMicroelectronics	—
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	4.5V	V
Current - Collector (Ic) (Max)	10mA	mA
Power - Max	45mW	mW
Noise Figure (Typ @ f)	1.1dB @ 1.8GHz	dB
Gain	19dB	dB
DC Current Gain (hFE) (Min) @ Ic, Vce	160 @ 5mA, 4V	—
Package / Case	SC-82A, SOT-343	—
Mounting Type	Surface Mount	—
Product Status	Obsolete	—
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level (MSL)	3 (168 Hours)	—

Substitute Part Grouping Explanation

Substitute parts for the START405TR are selected based on strict electrical and mechanical compatibility criteria. The primary substitution parameters are:

Critical Compatibility Parameters:

Transistor Type: NPN (required match)
Package / Case: SC-82A, SOT-343 (required match for PCB footprint compatibility)
Voltage - Collector Emitter Breakdown (Max): Must equal or exceed 4.5V
Current - Collector (Ic) (Max): Must equal or exceed 10mA
Power - Max: Must equal or exceed 45mW
Mounting Type: Surface Mount (required match)

Secondary Performance Parameters:

Noise Figure: Comparable performance at RF frequencies
Gain: Suitable for RF signal amplification
DC Current Gain (hFE): Adequate for circuit biasing requirements

Substitute parts are grouped into two categories based on voltage rating alignment:

Group 1: 5V Rated Devices — Parts with 5V collector-emitter breakdown voltage provide direct substitution with enhanced voltage margin. These include BFP405H6327XTSA1, BFP405H6740XTSA1, BFP410H6327XTSA1, BFP420H6327XTSA1, and BFP420H6801XTSA1.

Group 2: Higher Voltage/Performance Devices — Parts with voltage ratings above 5V (BFP450H6433XTMA1 at 5V, BFP540ESDH6327XTSA1 at 5V, BFP760H6327XTSA1 at 4V) offer enhanced RF performance characteristics including higher frequency capability and improved noise figures, suitable for applications requiring extended performance margins.

Non-Compatible Part: BFP196E6327HTSA1 operates at 12V with significantly different electrical characteristics and is not suitable as a direct substitute.

Parameter Comparison

Part Number	Manufacturer	Voltage (Max)	Ic (Max)	Power (Max)	Noise Figure (Typ)	Gain	hFE (Min)	Package	Status
START405TR	STMicroelectronics	4.5V	10mA	45mW	1.1dB @ 1.8GHz	19dB	160 @ 5mA, 4V	SOT-343	Obsolete
BFP405H6327XTSA1	Infineon Technologies	5V	25mA	75mW	1.25dB @ 1.8GHz	23dB	60 @ 5mA, 4V	SOT-343	Active
BFP405H6740XTSA1	Infineon Technologies	5V	25mA	75mW	1.25dB @ 1.8GHz	23dB	60 @ 5mA, 4V	SOT-343	Active
BFP410H6327XTSA1	Infineon Technologies	5V	40mA	150mW	1.2dB @ 2GHz	21.5dB	60 @ 13mA, 2V	SOT-343	Active
BFP420H6327XTSA1	Infineon Technologies	5V	35mA	160mW	1.1dB @ 1.8GHz	21dB	60 @ 20mA, 4V	SOT-343	Active
BFP420H6801XTSA1	Infineon Technologies	5V	35mA	160mW	1.1dB @ 1.8GHz	21dB	60 @ 20mA, 4V	SOT-343	Active
BFP450H6433XTMA1	Infineon Technologies	5V	100mA	450mW	1.25dB @ 1.8GHz	15.5dB	60 @ 50mA, 4V	SOT-343	Active
BFP540ESDH6327XTSA1	Infineon Technologies	5V	80mA	250mW	0.9dB ~ 1.4dB @ 1.8GHz	21.5dB	50 @ 20mA, 3.5V	SOT-343	Active
BFP760H6327XTSA1	Infineon Technologies	4V	70mA	240mW	0.5dB ~ 0.95dB @ 900MHz ~ 5.5GHz	16.5dB ~ 29dB	160 @ 35mA, 3V	SOT-343	Active

Engineering Selection Recommendations

Primary Substitutes (Direct Replacement Capability):

BFP420H6327XTSA1 and BFP420H6801XTSA1 are the closest functional equivalents to the START405TR. Both devices maintain the same noise figure specification (1.1dB @ 1.8GHz) as the original part, operate at 5V with enhanced voltage margin, and support higher collector currents (35mA) and power dissipation (160mW). These parts are manufactured by Infineon Technologies, carry Active product status, and are ROHS3 compliant with MSL 1 rating, providing superior moisture handling compared to the original MSL 3 specification. Both are available in SOT-343 packaging with surface mount compatibility.

Secondary Substitutes (Enhanced Performance):

BFP405H6327XTSA1 and BFP405H6740XTSA1 provide 5V operation with 25mA collector current capability and 75mW power dissipation. These devices offer improved gain (23dB) and are suitable for applications where the original 10mA current limit is insufficient. Both maintain Active status and ROHS3 compliance.

BFP540ESDH6327XTSA1 offers superior noise figure performance (0.9dB ~ 1.4dB @ 1.8GHz) with 80mA collector current capability and 250mW power dissipation, suitable for low-noise RF applications requiring extended performance margins.

BFP760H6327XTSA1 provides the closest voltage match (4V) to the original 4.5V specification with exceptional noise figure performance (0.5dB ~ 0.95dB across 900MHz to 5.5GHz) and high current capability (70mA). This device is recommended for applications requiring maximum RF performance and is available in high inventory (800,300 units).

Compliance and Availability:

All recommended substitute parts are manufactured by Infineon Technologies, carry Active product status, and are ROHS3 compliant. All substitute parts feature MSL 1 (Unlimited) moisture sensitivity rating, providing superior reliability compared to the original MSL 3 specification. Inventory availability ranges from 914 to 800,300 units across the substitute options.

Frequently Asked Questions (FAQ)

Q: Can BFP405H6327XTSA1 directly replace START405TR in existing designs?

A: BFP405H6327XTSA1 is electrically compatible with START405TR in terms of voltage rating (5V vs. 4.5V) and package (SOT-343). However, the collector current rating differs (25mA vs. 10mA). Direct substitution is possible if circuit biasing and current limiting are designed to operate within the original 10mA specification. The improved gain (23dB vs. 19dB) may require circuit tuning.

Q: What is the primary advantage of BFP420H6327XTSA1 over START405TR?

A: BFP420H6327XTSA1 maintains identical noise figure performance (1.1dB @ 1.8GHz) while providing 3.5× higher collector current capability (35mA vs. 10mA) and 3.6× higher power dissipation (160mW vs. 45mW). The device carries Active product status with superior MSL 1 moisture rating, ensuring long-term availability and reliability.

Q: Are all substitute parts available in the same SOT-343 package?

A: Yes. All substitute parts listed are manufactured in SC-82A SOT-343 surface mount packaging, ensuring PCB footprint compatibility with the original START405TR design.

Q: Why is BFP196E6327HTSA1 not recommended as a substitute?

A: BFP196E6327HTSA1 operates at 12V collector-emitter breakdown voltage, significantly exceeding the 4.5V specification of START405TR. This voltage rating mismatch, combined with different electrical characteristics (150mA collector current, 700mW power dissipation, 7.5GHz frequency), makes this device unsuitable for direct substitution in circuits designed for 4.5V operation.

Q: What is the difference between BFP405H6327XTSA1 and BFP405H6740XTSA1?

A: Both parts are electrically identical with 5V voltage rating, 25mA collector current, 75mW power dissipation, and SOT-343 packaging. The difference lies in inventory levels (40,333 units vs. 914 units) and supplier device package designation. Selection should be based on availability and supply chain requirements.

Q: Which substitute offers the best noise figure performance?

A: BFP760H6327XTSA1 provides the lowest noise figure specification (0.5dB ~ 0.95dB across 900MHz to 5.5GHz), making it the optimal choice for low-noise RF applications. This device also offers the highest inventory availability (800,300 units) and operates at 4V, closest to the original 4.5V specification.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All substitute parts carry ROHS3 compliance certification, meeting environmental and regulatory requirements equivalent to the original START405TR.

Q: What does MSL 1 (Unlimited) mean compared to the original MSL 3 (168 Hours)?

A: MSL (Moisture Sensitivity Level) indicates the maximum time a component can be exposed to moisture before soldering. MSL 1 (Unlimited) means the component has no moisture exposure time restriction, providing superior handling flexibility compared to the original MSL 3 specification, which limits exposure to 168 hours. All substitute parts offer this improved specification.

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