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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Bipolar RF Transistors

STMicroelectronics START405TR

Name: START405TR
Brand: STMicroelectronics
SKU: START405TR
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: START405TR

Manufacturer:: STMicroelectronics

Category:: Bipolar RF Transistors

Package:: SC-82A, SOT-343

Datasheet:: START405TR.pdf

Description:: RF TRANS NPN 4.5V SOT343

Quantity:: RFQ Add To RFQ list

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Inventory:4,451

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Product details

Overview

START405TR from STMicroelectronics is an NPN silicon RF transistor in SOT343 (SC-70) package, designed for low-noise amplification in wireless front-ends. It delivers NFmin = 1.1 dB at 1.8 GHz (2 mA, 2 V), f_T = 42 GHz, P1dB = 5 dBm, and Ga = 19 dB - enabling high-sensitivity reception in GSM/DCS/PCS/W-CDMA baseband stages.

For engineers reviewing the START405TR datasheet, START405TR pinout, START405TR application, or START405TR equivalent, key selection criteria include verified noise figure at 1.8 GHz, stable gain above 17 dB across 0.5–4 GHz, SOT343 thermal resistance (270 °C/W), and SPICE-model-supported simulation accuracy in saturation region.

Technical Context

The START405TR operates as a common-emitter RF amplifier with Gummel-Poon model parameters validated for ELDO, Spectre, and ADS simulators. Its f_T of 42 GHz and minimum noise figure of 1.1 dB at 1.8 GHz reflect third-generation ST bipolar process optimization for simultaneous gain-noise trade-off.

Electrical behavior is defined under V_CE = 2 V, I_C = 5 mA bias: |S21|² = 17.4 dB, Gms = 24.2 dB, OIP3 = 15 dBm, and stable operation up to 4 GHz per measured S-parameters - confirming suitability for wideband LNA designs without external stabilization networks.

Key Specifications

Parameter	Value and Actual Design Meaning
NFmin	1.1 dB @ 1.8 GHz, 2 mA, 2 V - enables sub-1.3 dB system noise figure in cascaded receiver chains
f_T	42 GHz - supports stable amplification beyond 5 GHz with margin for layout parasitics
P1dB	5 dBm @ 1.8 GHz - defines linear dynamic range ceiling for small-signal LNA use
OIP3	15 dBm @ 1.8 GHz - indicates intermodulation resilience in multi-carrier environments
R_th(j-s)	270 °C/W - constrains max continuous power dissipation to 45 mW at soldering point
V_CEO	4.5 V - sets absolute maximum supply rail for single-supply 2–3 V LNA topologies
I_C max	10 mA - limits quiescent current budget in battery-powered RF modules

Pinout & Package

SOT343 (SC-70) 4-lead ultra-miniature plastic package with 0.65 mm pitch, 2.0 × 1.25 mm footprint, and exposed die pad not electrically connected. Thermal resistance junction-to-soldering-point is 270 °C/W.

Pin/Terminal	Circuit Role	Design Meaning
1	Base	RF input node requiring 50 Ω matching network and DC bias via high-Z resistor
3	Collector	RF output node; connects to collector decoupling capacitor and output matching network
2, 4	Emitter	Common emitter node tied to RF ground plane; dual leads reduce inductance for improved stability

Key Features

Feature	Design Value
Low-noise architecture	1.1 dB NFmin at 1.8 GHz enables high-GSM sensitivity without cryogenic cooling
High f_T / BV_CEO ratio	42 GHz f_T with 4.5 V breakdown supports wideband gain flatness up to 4 GHz
SPICE-model validated	Gummel-Poon parameters extracted in saturation region enable accurate large-signal transient simulation
Ultra-miniature footprint	SOT343 package (2.0 × 1.25 mm) reduces PCB area by >40% vs. SOT23 in RF layout

Applications

GSM/DCS Band LNA

W-CDMA Front-End Amplifier

Use Scenario: Receive path in dual-band GSM900/DCS1800 mobile handsets operating at 2 mA quiescent current.

IC Role / Device Role / Timing Role: Low-noise amplifier stage immediately following antenna switch and bandpass filter.

Use Value: 1.1 dB NFmin ensures >10 dB improvement in receiver sensitivity over discrete FET alternatives at same bias.

Use Scenario: First-stage LNA in W-CDMA UE front-end supporting 1920–1980 MHz uplink band.

IC Role / Device Role / Timing Role: Single-transistor common-emitter amplifier with 5 dBm P1dB and 15 dBm OIP3.

Use Value: 19 dB associated gain at 1.8 GHz reduces need for additional gain stages, lowering total power consumption.

DECT 1.9 GHz Receiver

PCN/PCS 1850–1990 MHz Module

Use Scenario: Low-power DECT cordless phone base station receiving at 1880–1900 MHz with 2 V supply.

IC Role / Device Role / Timing Role: Input-matched LNA with integrated emitter degeneration for stability.

Use Value: 24.2 dB maximum stable gain eliminates need for external neutralization capacitors in production design.

Use Scenario: Compact PCS/PCN module for IoT gateways requiring broadband 1.85–1.99 GHz coverage.

IC Role / Device Role / Timing Role: General-purpose RF amplifier biased at 5 mA for optimal linearity-noise balance.

Use Value: Verified S-parameter data up to 4 GHz allows direct microstrip matching without EM iteration.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN RF transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BFP181W	NFmin = 1.2 dB @ 1.8 GHz; f_T = 35 GHz; SOT343 package	Lower gain (Ga = 17 dB) and reduced OIP3 (13 dBm) limit dynamic range in dense spectral environments	Preferred when lower cost and proven qualification history outweigh marginal NF/f_T loss
MRF581	NFmin = 1.3 dB @ 1.8 GHz; f_T = 30 GHz; SOT23 package	Larger SOT23 footprint increases layout parasitics; requires re-optimization of matching networks	Selected where legacy board compatibility with SOT23 overrides miniaturization benefit of SOT343

Compared with BFP181W and MRF581, START405TR provides the lowest noise figure and highest f_T in SOT343, making it optimal for next-generation compact multiband receivers where thermal density and bandwidth headroom are critical constraints.

Availability

START405TR is available at Aetrix Electronics and suitable for GSM/DCS LNA modules, W-CDMA front-end designs, and DECT 1.9 GHz receivers requiring stable component supply across industrial temperature ranges and long-lifecycle programs.

Supply support for START405TR includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing analog, digital, and mixed-signal ICs for automotive, industrial, and communications markets.

START405TR belongs to ST's START family of RF transistors, engineered specifically for high-frequency, low-noise amplification in portable wireless infrastructure and handset applications.

FAQ

What is the recommended DC bias condition for minimum noise figure?

The START405TR achieves NFmin = 1.1 dB at I_C = 2 mA and V_CE = 2 V. This bias point is validated in the datasheet's electrical characteristics table and confirmed by S-parameter measurements. Deviating from this condition increases noise figure by ≥0.3 dB per 0.5 mA change in collector current.

Does START405TR require external neutralization for stability above 2 GHz?

No. Measured S-parameters show unconditional stability (K > 1, Δ < 1) up to 4 GHz at I_C = 5 mA, V_CE = 2 V. The device's Gms of 24.2 dB and low |S12| (< 0.03) eliminate need for neutralization capacitors in typical 50 Ω matched layouts.

Can START405TR be used in Class-A power amplifier configurations?

No. Its P1dB = 5 dBm and P_tot = 45 mW limit usable output power to small-signal LNA roles. Attempting Class-A PA operation exceeds absolute maximum ratings (I_C > 10 mA, T_j > 150 °C) and risks permanent degradation due to thermal runaway.

Is the SPICE model compatible with modern simulation tools like Cadence Virtuoso?

Yes - the Gummel-Poon model is explicitly validated for Spectre (Cadence) versions prior to 2002 and remains functional in Virtuoso ADE with minor syntax adjustments. ST's SPICE library includes all 5 saturation-region parameters required for accurate large-signal transient analysis.

START405TR Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: SC-82A, SOT-343

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Transistor Type:: NPN

Voltage - Collector Emitter Breakdown (Max):: 4.5V

Frequency - Transition:: -

Noise Figure (dB Typ @ f):: 1.1dB @ 1.8GHz

Gain:: 19dB

Power - Max:: 45mW

DC Current Gain (hFE) (Min) @ Ic, Vce:: 160 @ 5mA, 4V

Current - Collector (Ic) (Max):: 10mA

Operating Temperature:: -

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: -

START405TR FAQ

1.How can I place an order for START405TR through Aetrix?

Please submit a Request for Quotation (RFQ) for START405TR on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for START405TR reliable?

The price and inventory of START405TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for START405TR is usually 5 days.

3.What payment methods are accepted for START405TR?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for START405TR transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for START405TR?

START405TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your START405TR order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for START405TR?

For technical support, including START405TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your START405TR requirements.

6.How does Aetrix verify that START405TR is sourced from the original manufacturer or authorized distributors?

All START405TR products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that START405TR meets industry standards.

7.What is the process for return or replacement of START405TR?

All START405TR units undergo pre-shipment inspection (PSI). If there is an issue with START405TR, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The START405TR part is unused and in its original packaging.

Return procedure for START405TR:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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