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

STMicroelectronics SD1477

Name: SD1477
Brand: STMicroelectronics
SKU: SD1477
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SD1477

Manufacturer:: STMicroelectronics

Category:: Bipolar RF Transistors

Package:: M111

Datasheet:: SD1477.pdf

Description:: RF TRANS NPN 18V M111

Quantity:: RFQ Add To RFQ list

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Inventory:9,655

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Product details

Overview

SD1477 from STMicroelectronics is a 12.5 V, 100 W Class C NPN RF bipolar transistor in M111 plastic package, designed for VHF FM mobile transmitters operating at 136–175 MHz with 6.0 dB power gain and internal input matching. It features diffused emitter resistors for high-VSWR ruggedness and is rated for 20 A collector current and 270 W power dissipation.

For engineers reviewing the SD1477 datasheet, SD1477 pinout, SD1477 application, or SD1477 equivalent, key selection criteria include its 175 MHz frequency capability, common-emitter configuration, 0.65 °C/W junction-to-case thermal resistance, and impedance-matched operation at 12.5 V supply in VHF land-mobile radio systems.

Technical Context

The SD1477 operates as a common-emitter Class C amplifier optimized for fixed-frequency VHF FM transmission. Its epitaxial silicon planar structure supports 18 V V_CEO, 36 V V_CBO/V_CES, and 4.0 V V_EBO, enabling robust switching under high RF stress.

Internal input matching delivers stable 6.0 dB gain across 136–175 MHz with Z_IN = 1.5 – j0.9 Ω and Z_CL = 0.5 – j1.0 Ω at 175 MHz, while diffused emitter resistors sustain operation under 10:1 VSWR without degradation.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	18 V - maximum safe collector-emitter voltage under DC bias, defining rail limit for Class C stage design
P_OUT	100 W min - RF output power at 175 MHz, 12.5 V, 25 W drive, enabling high-power mobile transmitter stages
G_P	6.0 dB - small-signal power gain at full rated output, directly determining driver stage sizing
R_TH(j-c)	0.65 °C/W - thermal resistance from junction to case, requiring heatsink interface ≤0.35 °C/W for 200°C max T_J
C_OB	350 pF - collector-base capacitance at 12.5 V, critical for tank circuit tuning and stability margin
f_max	Not specified - device optimized for fundamental VHF operation, not broadband or UHF use

Pinout & Package

M111 is a 4-terminal plastic epoxy-sealed package with metalized baseplate for thermal conduction and mechanical mounting. Dimensions: 24.8 mm × 5.5 mm × 4.1 mm (L×W×H), with two emitter leads for low-inductance current return.

Pin/Terminal	Circuit Role	Design Meaning
1	Collector	Main RF power output node; electrically and thermally connected to metal tab/baseplate
2	Base	RF input control terminal; requires external matching network per Z_IN = 1.5 – j0.9 Ω at 175 MHz
3 & 4	Emitter	Dual low-inductance emitter returns; both must be bonded to ground plane for thermal and RF stability

Key Features

Feature	Design Value
Diffused emitter resistors	Enable survivability under 10:1 VSWR at full rated power, eliminating need for external circulators in mobile base stations
Internally input-matched	Reduces external matching complexity across 136–175 MHz, lowering bill-of-materials and layout sensitivity
Common-emitter Class C topology	Delivers high efficiency (>65%) in FM modulation schemes with fixed carrier frequency, minimizing thermal load
M111 plastic package with baseplate	Provides 0.65 °C/W R_TH(j-c) and mechanical rigidity for chassis-mounting in vehicular RF enclosures

Applications

VHF FM Mobile Transmitter

Land-Mobile Radio Base Station

Use Scenario: High-reliability FM voice transmission in police/fire/emergency vehicle radios operating at 150–174 MHz.

IC Role / Device Role / Timing Role: Final-stage RF power amplifier delivering 100 W P_OUT into 50 Ω load with 6.0 dB gain.

Use Value: Diffused emitter resistors withstand antenna mismatch during vehicle motion, preventing catastrophic failure without external protection.

Use Scenario: Fixed-site repeater transmitter amplifying low-level IF/RF signals for wide-area coverage in rural public safety networks.

IC Role / Device Role / Timing Role: Class C linearized PA stage biased for constant-envelope FM, leveraging internal input match for stable gain flatness.

Use Value: 0.65 °C/W thermal resistance enables forced-air cooling instead of liquid cooling, reducing system size and cost.

Amateur Radio HF/VHF Amplifier

Marine VHF Communications

Use Scenario: Home-built 2-meter band (144–148 MHz) linear amplifier used by licensed amateur operators for long-distance SSB/FM contacts.

IC Role / Device Role / Timing Role: High-efficiency final amplifier driven by solid-state driver stage, operating at 12.5 V DC supply.

Use Value: Z_IN = 1.5 – j0.9 Ω at 144 MHz simplifies L-network design, improving build repeatability and tuning speed.

Use Scenario: Shipboard VHF transceiver (156–162 MHz) requiring salt-spray-resistant, vibration-tolerant RF power stage for distress and navigation traffic.

IC Role / Device Role / Timing Role: Ruggedized final PA handling intermittent high-duty-cycle transmissions in harsh marine environments.

Use Value: Dual emitter terminals reduce ground loop inductance, maintaining stability during engine ignition noise events.

Equivalent & Alternatives

The following parts are listed as comparable options for similar VHF RF power amplifier applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
MRF454	Higher V_CEO (35 V), lower P_OUT (60 W), TO-220AB package, no internal input match	Requires full external matching network; suited for variable-frequency or multi-band designs	Select when wider frequency agility or higher voltage headroom is required over fixed 136–175 MHz operation
BLF244	Same M111 package, 28 V V_CEO, 125 W P_OUT, but 28 V supply requirement and different Z_IN (2.0 – j1.2 Ω)	Designed for 28 V mobile systems; incompatible with 12.5 V bias architecture without redesign	Choose only if upgrading from 12.5 V to 28 V platform and retuning matching networks

Compared with MRF454 and BLF244, the SD1477 uniquely combines 12.5 V operation, internal 136–175 MHz input match, and dual-emitter ruggedness-making it irreplaceable in legacy 12 V vehicular FM transmitters without circuit rework.

Availability

SD1477 is available at Aetrix Electronics and suitable for VHF FM mobile transmitters, land-mobile radio base stations, amateur radio amplifiers, and marine communications equipment requiring stable component supply despite its obsolete status.

Supply support for SD1477 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 manufacturer headquartered in Geneva, Switzerland, specializing in power devices, analog ICs, microcontrollers, and RF components for industrial, automotive, and communications markets.

The SD1477 belongs to ST's legacy RF bipolar transistor product line, engineered specifically for high-reliability, high-power VHF mobile radio infrastructure where ruggedness and thermal performance outweigh integration density.

FAQ

Is SD1477 still in active production?

No, SD1477 is marked "Obsolete Product(s)" in the official STMicroelectronics datasheet revision history. However, Aetrix Electronics maintains verified legacy stock with full traceability and provides engineering support for continued use in maintenance and replacement programs.

Can SD1477 be used at frequencies outside 136–175 MHz?

The device is characterized and matched only within 136–175 MHz. At 108 MHz or 220 MHz, gain drops >3 dB and output power falls below 70 W due to impedance mismatch and reduced f_T margin; operation outside this band is not supported by ST's specifications.

What is the recommended heatsink interface for SD1477?

A thermal interface material with ≤0.15 °C·in²/W resistance (e.g., Parker Chomerics THERM-A-GAP G30) is required between the M111 metal baseplate and heatsink to maintain junction temperature ≤200°C at 100 W P_OUT, given its 0.65 °C/W R_TH(j-c).

Does SD1477 require external bias sequencing?

No sequencing is specified. The device operates in Class C with fixed DC bias applied simultaneously to collector (12.5 V) and base (via RF choke or DC feed). Emitter terminals must be DC-grounded through low-inductance paths to prevent oscillation.

SD1477 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: M111

Packaging:: Tray

Product Status:: Obsolete

Transistor Type:: NPN

Voltage - Collector Emitter Breakdown (Max):: 18V

Frequency - Transition:: -

Noise Figure (dB Typ @ f):: -

Gain:: 6dB

Power - Max:: 270W

DC Current Gain (hFE) (Min) @ Ic, Vce:: 10 @ 5A, 5V

Current - Collector (Ic) (Max):: 20A

Operating Temperature:: 200°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: M111

SD1477 FAQ

1.How can I place an order for SD1477 through Aetrix?

Please submit a Request for Quotation (RFQ) for SD1477 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 SD1477 reliable?

The price and inventory of SD1477 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SD1477 is usually 5 days.

3.What payment methods are accepted for SD1477?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SD1477 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SD1477?

SD1477 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SD1477 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 SD1477?

For technical support, including SD1477 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SD1477 requirements.

6.How does Aetrix verify that SD1477 is sourced from the original manufacturer or authorized distributors?

All SD1477 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 SD1477 meets industry standards.

7.What is the process for return or replacement of SD1477?

All SD1477 units undergo pre-shipment inspection (PSI). If there is an issue with SD1477, 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 SD1477 part is unused and in its original packaging.

Return procedure for SD1477:

1.Submit a request within 90 days.

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

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