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

Diodes Incorporated FMMT634TC

Name: FMMT634TC
Brand: Diodes Incorporated
SKU: FMMT634TC
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: FMMT634TC

Manufacturer:: Diodes Incorporated

Category:: Single Bipolar Transistors

Package:: TO-236-3, SC-59, SOT-23-3

Datasheet:: FMMT634TC.pdf

Description:: TRANS NPN DARL 100V 0.9A SOT23-3

Quantity:: RFQ Add To RFQ list

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Inventory:3,513

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Product details

Overview

FMMT634 from Diodes Incorporated is a 100V NPN Darlington transistor in SOT23 package, designed for high-voltage switching with BV_CEO = 100 V, I_C = 900 mA continuous, and h_FE ≥ 5,000 at 2 A - enabling robust relay and solenoid drive in space-constrained industrial control modules.

For engineers reviewing the FMMT634 datasheet, FMMT634 pinout, FMMT634 application, or FMMT634 equivalent, key selection criteria include high-voltage breakdown margin (100 V), Darlington current gain stability up to 2 A, SOT23 thermal derating behavior, and AEC-Q101 qualification for automotive-grade reliability.

Technical Context

This Darlington pair integrates two NPN transistors in cascade to deliver high DC current gain while maintaining single-device simplicity. It operates with V_BE(sat) = 1.5–1.65 V at I_C = 1 A and exhibits V_CE(sat) ≤ 0.85 V at I_C = 900 mA / I_B = 5 mA - critical for low-loss switching in inductive load interfaces.

The device supports pulsed operation up to I_CM = 5 A and features f_T = 140 MHz, confirming suitability for moderate-speed switching (e.g., <50 kHz PWM) rather than RF amplification. Its safe operating area (SOA) is defined up to 100 V and 1 A under DC conditions, with thermal resistance R_θJA = 200 °C/W on standard FR4.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	100 V - enables direct interface with 24–48 V industrial bus systems without external snubbing
I_C (continuous)	900 mA - sufficient to drive 12 V/500 mW relays or 24 V/1 W solenoids continuously
h_FE	≥5 k at 2 A - ensures low base drive current requirement (≤200 µA per mA of collector current)
P_D	625 mW - limits steady-state power in SOT23; requires PCB copper area for >500 mW dissipation
V_CE(sat)	0.75 V max at I_C = 900 mA - reduces conduction loss to <0.68 W, easing thermal design
AEC-Q101	Qualified - validated for automotive under-hood temperature cycling (-55°C to +150°C)

Pinout & Package

SOT23-3 plastic surface-mount package with matte tin-plated leads; 0.008 g mass; UL 94V-0 flammability rating; moisture sensitivity level 1.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	E	Reference node for base-emitter junction; connects to ground or low-side return path
2 (Base)	B	Control input; requires current-limited drive (e.g., 5 mA typical for 900 mA output)
3 (Collector)	C	High-side switch node; rated for 100 V standoff and 900 mA continuous current

Key Features

Feature	Design Value
High-voltage Darlington architecture	Enables 100 V load switching with single-device simplicity and no external bias network
Low saturation voltage	V_CE(sat) ≤ 0.85 V at full rated current minimizes heat generation in compact layouts
AEC-Q101 qualification	Validated for automotive applications including body electronics and power distribution modules
Green, halogen-free construction	Meets RoHS 2 and JEDEC J-STD-020 Level 1 standards for lead-free assembly compatibility

Applications

Lamp Driving

Relay Control

Use Scenario: Switching 12 V/21 W automotive brake lamps in body control modules.

IC Role / Device Role / Timing Role: High-side NPN Darlington switch controlling lamp current path to ground.

Use Value: 100 V V_CEO accommodates load dump transients; 900 mA I_C exceeds lamp surge current.

Use Scenario: Driving 24 V/400 mW signal relays in programmable logic controllers.

IC Role / Device Role / Timing Role: Low-base-drive-current switch interfacing microcontroller GPIO to relay coil.

Use Value: h_FE ≥ 5k allows 1 mA base current to switch 5 A relay coils reliably.

Solenoid Actuation

Industrial Sensor Interface

Use Scenario: Controlling 24 V/1.2 W pneumatic valve solenoids in factory automation I/O modules.

IC Role / Device Role / Timing Role: Inductive load switch with integrated flyback energy handling via V_CEO margin.

Use Value: 5 A I_CM supports solenoid turn-on surge; SOA curve validates 100 ms pulse capability.

Use Scenario: Isolating and amplifying analog sensor outputs (e.g., pressure transducers) in 4–20 mA loop drivers.

IC Role / Device Role / Timing Role: Current gain stage boosting weak sensor signals before DAC or op-amp conditioning.

Use Value: Stable h_FE across 10 mA–2 A range ensures linear current transfer in feedback paths.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
ZTX1048A	V_CEO = 80 V, h_FE = 1,000–2,500 at 500 mA - lower voltage rating and gain	Not suitable for 100 V bus systems; limited to ≤48 V designs	Select only when board-level clamping protects against transients
MMDT3904-7-F	Single NPN, V_CEO = 40 V, h_FE = 100–300 - no Darlington gain or voltage headroom	Requires external base resistor network and higher drive current	Use only in low-voltage, low-power signal switching where gain and voltage are not critical

Compared with ZTX1048A and MMDT3904-7-F, FMMT634 delivers unique combination of 100 V standoff, Darlington gain ≥5k, and AEC-Q101 qualification - making it irreplaceable in automotive and industrial high-voltage switching where single-device simplicity and reliability are mandatory.

Availability

FMMT634 is available at Aetrix Electronics and suitable for lamp driving, relay control, solenoid actuation, and industrial sensor interface applications requiring stable component supply and long-term lifecycle support.

Supply support for FMMT634 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, with design centers across Asia and Europe.

FMMT634 belongs to Diodes' high-reliability discrete transistor product line, engineered specifically for automotive and industrial switching applications demanding extended temperature range, high-voltage tolerance, and AEC-Q101 compliance.

FAQ

What is the maximum continuous collector current for FMMT634?

The FMMT634 supports 900 mA continuous collector current at T_A = +25°C with proper PCB copper heatsinking. Derating begins above 25°C ambient, reaching zero at +150°C junction temperature per the published derating curve. This rating assumes mounting on 25 mm × 25 mm 1 oz copper on FR4.

Is FMMT634 pin-compatible with its PNP complement?

Yes - FMMT634 (NPN) and FMMT734 (PNP) share identical SOT23-3 pinout (E-B-C), enabling symmetrical high-side/low-side driver designs. Both devices maintain matching V_CEO/V_ECO, h_FE, and thermal characteristics, simplifying layout and BOM consolidation.

Can FMMT634 be used in PWM motor control?

FMMT634 supports PWM frequencies up to ~20 kHz based on t_on = 290 ns and t_off = 2.4 µs, but its 2.4 µs turn-off time limits efficiency above 10 kHz in high-current (>500 mA) loads. For >20 kHz operation, consider faster-switching alternatives like MOSFETs.

Does FMMT634 require a base resistor in all applications?

Yes - a series base resistor is mandatory to limit I_B and prevent thermal runaway. For 900 mA I_C, minimum h_FE = 5,000 implies I_B ≥ 180 µA; typical design uses 1–5 mA base drive, requiring 1–5 kΩ resistor from 5 V MCU GPIO, depending on required switching speed.

FMMT634TC Specifications

Product attributes: Attribute value

Manufacturer:: Diodes Incorporated

Series:: -

Package/Case:: TO-236-3, SC-59, SOT-23-3

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Transistor Type:: NPN - Darlington

Current - Collector (Ic) (Max):: 900 mA

Voltage - Collector Emitter Breakdown (Max):: 100 V

Vce Saturation (Max) @ Ib, Ic:: 960mV @ 5mA, 1A

Current - Collector Cutoff (Max):: 100nA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 20000 @ 100mA, 5V

Power - Max:: 625 mW

Frequency - Transition:: 140MHz

Operating Temperature:: -55°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-3

FMMT634TC FAQ

1.How can I place an order for FMMT634TC through Aetrix?

Please submit a Request for Quotation (RFQ) for FMMT634TC 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 FMMT634TC reliable?

The price and inventory of FMMT634TC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for FMMT634TC is usually 5 days.

3.What payment methods are accepted for FMMT634TC?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for FMMT634TC transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for FMMT634TC?

FMMT634TC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your FMMT634TC 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 FMMT634TC?

For technical support, including FMMT634TC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your FMMT634TC requirements.

6.How does Aetrix verify that FMMT634TC is sourced from the original manufacturer or authorized distributors?

All FMMT634TC 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 FMMT634TC meets industry standards.

7.What is the process for return or replacement of FMMT634TC?

All FMMT634TC units undergo pre-shipment inspection (PSI). If there is an issue with FMMT634TC, 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 FMMT634TC part is unused and in its original packaging.

Return procedure for FMMT634TC:

1.Submit a request within 90 days.

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

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