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

STMicroelectronics MD1803DFX

Name: MD1803DFX
Brand: STMicroelectronics
SKU: MD1803DFX
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: MD1803DFX

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-3P-3 Full Pack

Datasheet:: MD1803DFX.pdf

Description:: TRANS NPN 700V 10A TO-3PF

Quantity:: RFQ Add To RFQ list

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Product details

Overview

MD1803DFX from STMicroelectronics is a high-voltage NPN power transistor with integrated freewheeling diode, designed specifically for horizontal deflection output stages in standard-definition CRT television displays. It features V_CES = 1500 V, I_C = 10 A, P_TOT = 57 W at T_C = 25°C, h_FE = 5.5–18 (at I_C = 1–5 A), and U.L.-compliant ISOWATT218FX insulated package.

For engineers reviewing the MD1803DFX datasheet, MD1803DFX pinout, MD1803DFX application, or MD1803DFX equivalent, key selection criteria include high-voltage switching capability (V_CES = 1500 V), low base drive requirement (I_B(sat) = 1.25 A @ I_C = 5 A), tight h_FE spread, integrated diode forward voltage (V_f = 1.6 V @ I_F = 5 A), and thermal resistance (R_thj-case ≤ 2.2 °C/W).

Technical Context

The MD1803DFX employs diffused collector planar technology with an enhanced high-voltage structure optimized for inductive flyback energy recovery in CRT horizontal deflection circuits. Its integrated freewheeling diode enables self-contained commutation without external diode placement, reducing layout complexity and parasitic inductance.

It operates under pulsed conditions (t_P = 300 µs, duty cycle ≤ 1.5%) with storage time t_s = 2.5–3 µs and fall time t_f = 0.3–0.6 µs at f_h = 16 kHz, supporting stable line-scan timing while maintaining SOA integrity under reverse-biased switching stress.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CES	1500 V - Withstands full CRT flyback voltage without breakdown during retrace.
I_C	10 A continuous - Sustains peak horizontal scan current in SD-CRT applications.
P_TOT	57 W at T_C = 25°C - Enables high-power deflection stage operation with heatsink mounting.
h_FE	5.5–18 - Tight DC gain range ensures consistent base drive design across production lots.
V_f (diode)	1.6 V @ I_F = 5 A - Integrated diode minimizes conduction loss during flyback recovery.
R_thj-case	≤2.2 °C/W - Supports efficient thermal transfer to external heatsink in compact TV chassis.
t_s/t_f	2.5–3 µs / 0.3–0.6 µs - Fast switching preserves linearity and reduces switching loss at 16 kHz.

Pinout & Package

The MD1803DFX is housed in the fully insulated ISOWATT218FX package, compliant with U.L. insulation requirements (V_isol = 2500 V rms from all leads to heatsink). The package provides mechanical robustness and thermal performance suitable for high-reliability CRT deflection modules.

Pin/Terminal	Circuit Role	Design Meaning
Collector (C)	Main high-voltage power switch node	Connected to CRT flyback transformer primary; withstands 1500 V transient spikes.
Base (B)	Control input for saturation switching	Driven with ~1.25 A to ensure full saturation at 5 A collector current.
Emitter (E)	Power return and diode cathode	Common node for transistor emitter and integrated diode anode; referenced to ground in typical deflection circuit.

Key Features

Feature	Design Value
Integrated freewheeling diode	Eliminates need for external diode, reducing PCB area and parasitic loop inductance.
Diffused collector "enhanced generation"	Improves silicon efficiency and SOA margin under high-voltage inductive switching.
Tight h_FE range (5.5–18)	Reduces base drive design margining and improves consistency of scan linearity.
U.L.-compliant insulation	Enables direct mounting to grounded heatsink without isolation hardware.
ECOPACK® lead-free construction	Meets RoHS compliance requirements for consumer electronics manufacturing.

Applications

TV Horizontal Deflection Stage

SD-CRT Monitor Output

Use Scenario: Horizontal scanning in analog NTSC/PAL CRT TVs requiring precise 15.625 kHz line retrace timing.

IC Role / Device Role / Timing Role: High-voltage NPN switch driving flyback transformer primary; controls energy storage and release per scan line.

Use Value: Integrated diode and low V_CE(sat) (2 V) minimize switching loss and improve thermal stability during sustained operation.

Use Scenario: Line-output stage in professional SD-CRT monitors used in broadcast or medical imaging equipment.

IC Role / Device Role / Timing Role: Primary power switch in resonant horizontal deflection circuit; handles repetitive 16 kHz inductive load switching.

Use Value: Tight h_FE tolerance and stable performance over temperature ensure consistent scan amplitude and geometry across operating range.

Legacy CRT Video Projector

Service Replacement Module

Use Scenario: Horizontal deflection in three-tube CRT video projectors where reliability and long-term parameter stability are critical.

IC Role / Device Role / Timing Role: High-energy switching element managing flyback pulse generation and damping via integrated diode.

Use Value: R_thj-case ≤ 2.2 °C/W and V_isol = 2500 V rms support safe, thermally managed operation in enclosed optical chassis.

Use Scenario: Drop-in replacement for failed horizontal output transistors in field-service CRT TV repair.

IC Role / Device Role / Timing Role: Direct-fit mechanical and electrical replacement for legacy MD1803 series in ISOWATT218FX socketed designs.

Use Value: Identical pinout, package outline, and absolute ratings enable zero-modification board-level replacement.

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage horizontal deflection transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BU2520DX	V_CES = 1500 V, I_C = 10 A, but no integrated diode; R_thj-case = 2.5 °C/W	Requires external freewheeling diode and larger heatsink area	Select when diode selection or thermal layout flexibility is prioritized over integration.
2SC5411	V_CES = 1500 V, I_C = 8 A, h_FE = 6–12, no integrated diode, TO-3P package	Lacks insulation rating and integrated diode; different mechanical footprint	Use only with redesign of mounting and diode placement; not drop-in compatible.

Compared with BU2520DX and 2SC5411, the MD1803DFX offers unique integration of insulation, diode, and tighter h_FE, enabling simplified, space-constrained CRT deflection designs without compromising SOA or thermal performance.

Availability

MD1803DFX is available at Aetrix Electronics and suitable for CRT television manufacturing, SD-CRT monitor production, and legacy display service programs requiring stable component supply and long-lifecycle support.

Supply support for MD1803DFX 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, Switzerland, specializing in power discrete devices, automotive ICs, microcontrollers, and analog/mixed-signal solutions.

The MD product series was developed specifically for CRT horizontal deflection applications, emphasizing high-voltage ruggedness, integrated functionality, and thermal reliability in consumer display systems.

FAQ

Is MD1803DFX pin-compatible with earlier MD1803 variants?

Yes - MD1803DFX retains identical pinout, package outline (ISOWATT218FX), and terminal assignments as prior MD1803 versions. The 'F' suffix denotes ECOPACK® lead-free construction and updated h_FE limits per Rev 6, with no mechanical or electrical interface changes.

Can MD1803DFX be used in modern LCD or LED TV power supplies?

No - MD1803DFX is optimized for 15–16 kHz horizontal deflection in CRT systems, not SMPS operation. Its safe operating area, switching timing, and V_CEO = 700 V rating make it unsuitable for high-frequency, high-efficiency switch-mode power conversion found in modern displays.

What is the significance of the "DFX" suffix in MD1803DFX?

The "DFX" suffix indicates the device uses Diffused Collector planar technology ("D"), incorporates an integrated freewheeling diode ("F"), and is packaged in the ISOWATT218FX insulated housing ("X"). This distinguishes it from non-diode or non-insulated variants in the MD1803 family.

Does MD1803DFX require a heatsink, and what mounting torque is recommended?

Yes - due to P_TOT = 57 W, a properly sized heatsink is mandatory. ST specifies M3 screw mounting with 0.5–0.7 N·m torque for the ISOWATT218FX package. Thermal interface material must be applied uniformly to maintain R_thj-case ≤ 2.2 °C/W performance.

MD1803DFX Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-3P-3 Full Pack

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

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

Voltage - Collector Emitter Breakdown (Max):: 700 V

Vce Saturation (Max) @ Ib, Ic:: 2V @ 1.25A, 5A

Current - Collector Cutoff (Max):: 200µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 5.5 @ 5A, 5V

Power - Max:: 57 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-3PF

MD1803DFX FAQ

1.How can I place an order for MD1803DFX through Aetrix?

Please submit a Request for Quotation (RFQ) for MD1803DFX 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 MD1803DFX reliable?

The price and inventory of MD1803DFX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MD1803DFX is usually 5 days.

3.What payment methods are accepted for MD1803DFX?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MD1803DFX transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for MD1803DFX?

MD1803DFX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your MD1803DFX 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 MD1803DFX?

For technical support, including MD1803DFX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MD1803DFX requirements.

6.How does Aetrix verify that MD1803DFX is sourced from the original manufacturer or authorized distributors?

All MD1803DFX 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 MD1803DFX meets industry standards.

7.What is the process for return or replacement of MD1803DFX?

All MD1803DFX units undergo pre-shipment inspection (PSI). If there is an issue with MD1803DFX, 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 MD1803DFX part is unused and in its original packaging.

Return procedure for MD1803DFX:

1.Submit a request within 90 days.

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

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