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

onsemi NSCT817-25LT3G

Name: NSCT817-25LT3G
Brand: onsemi
SKU: NSCT817-25LT3G
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: NSCT817-25LT3G

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: NSCT817-25LT3G.pdf

Description:: TRANS NPN 45V 0.5A SOT23-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

NSCT817-25LT3G from onsemi is an NPN silicon general-purpose transistor in SOT-23 package, rated for V_CEO = 45 V, I_C = 500 mA, and h_FE = 160–400 (at I_C = 100 mA, V_CE = 1.0 V). It delivers V_CE(sat) ≤ 0.7 V at I_C/I_B = 10 and f_T = 100 MHz, supporting switching and amplification in compact DC-DC feedback paths and LED driver stages.

For engineers reviewing the NSCT817-25LT3G datasheet, pinout, applications, or equivalent options, key selection criteria include verified h_FE binning (−25 variant), SOT-23 thermal performance (R_JA = 556°C/W on FR-5), and Pb-free compliance per J-STD-609.

Technical Context

This device operates as a medium-current, medium-voltage NPN switch with guaranteed DC current gain across production lots-specifically binned to h_FE ≥ 160 at 100 mA/1 V and ≥ 40 at 500 mA/1 V. Its 100 MHz f_T supports stable operation in low-frequency switching regulators and signal buffering up to ~10 MHz.

The SOT-23 package enables surface-mount integration with defined thermal derating: 1.8 mW/°C above 25°C on FR-5 board (225 mW max), and 2.4 mW/°C on alumina (300 mW max). Junction temperature range is −55°C to +150°C, validated for industrial ambient conditions.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	45 V - Maximum safe collector-emitter voltage before breakdown; sets upper rail limit in 24 V and 36 V supply switching circuits.
I_C (continuous)	500 mA - Continuous collector current handling; sufficient for driving small relays, logic-level MOSFET gates, or LED strings up to 200 mA with margin.
h_FE (100 mA, 1 V)	160–400 - Guaranteed DC current gain range ensures predictable base drive sizing for saturation in linear and switching modes.
V_CE(sat) (500 mA, 50 mA)	≤ 0.7 V - Low saturation voltage minimizes power loss (≤ 350 mW) and self-heating during high-duty-cycle switching.
f_T	100 MHz - Transition frequency confirms usable bandwidth for audio preamps, PWM error amplifiers, and low-speed digital signal conditioning.
R_JA (FR-5)	556 °C/W - Thermal resistance defines junction-to-ambient rise under PCB layout constraints; requires minimal copper pour for <100°C rise at full load.

Pinout & Package

SOT-23 (Case 318, Style 6) - 3-pin surface-mount plastic package with standard lead pitch (0.95 mm), body dimensions 2.90 × 1.30 × 1.00 mm, and Pb-free matte tin plating. Pin 1 = Base, Pin 2 = Emitter, Pin 3 = Collector.

Pin/Terminal	Circuit Role	Design Meaning
1 (Base)	Control input	Receives current-limited drive to bias transistor into active or saturated region; requires series resistor to limit I_B based on h_FE and target I_C.
2 (Emitter)	Current return path	Connected to ground or low-side reference; forms common node for current sensing and feedback in emitter-follower or switch configurations.
3 (Collector)	Output current terminal	Switches load between supply rail and emitter; must be routed with adequate trace width to handle 500 mA without excessive IR drop or heating.

Key Features

Feature	Design Value
Pb-free construction	Complies with J-STD-609 Class 3 moisture sensitivity and RoHS Directive 2011/65/EU; qualified for reflow per IPC-J-STD-020.
h_FE binning (−25)	Guaranteed minimum h_FE = 160 at 100 mA/1 V ensures consistent base drive requirements across production lots.
Low V_CE(sat)	≤ 0.7 V at I_C = 500 mA enables efficient switching in battery-powered and thermally constrained applications.
High f_T	100 MHz transition frequency supports stable closed-loop response in analog feedback networks and broadband signal amplification.

Applications

DC-DC Converter Feedback	LED Constant-Current Driver
Use Scenario: Used in optocoupler-coupled secondary-side error amplifiers of isolated flyback converters. IC Role / Device Role / Timing Role: NPN transistor amplifies error signal to drive optocoupler LED, enabling precise output voltage regulation. Use Value: High h_FE and low V_CE(sat) ensure accurate current transfer ratio and minimal dropout across line/load variations.	Use Scenario: Implements constant-current sink for indicator LEDs in industrial HMI panels. IC Role / Device Role / Timing Role: Acts as adjustable current sink controlled by DAC or microcontroller GPIO via base resistor. Use Value: Tight h_FE binning allows predictable current setting with ±5% tolerance using standard 1% resistors.
Microcontroller GPIO Expander	Small-Signal Amplifier Stage
Use Scenario: Drives 12 V relay coils from 3.3 V MCU outputs in programmable logic controllers. IC Role / Device Role / Timing Role: Level-shifting switch translating low-voltage logic to higher-voltage load control. Use Value: 45 V V_CEO rating provides margin against inductive kickback; fast turn-off minimizes coil release delay.	Use Scenario: First-stage preamplifier in sensor signal conditioning for pressure transducers. IC Role / Device Role / Timing Role: Provides voltage gain with low noise and stable bias point in common-emitter configuration. Use Value: 100 MHz f_T and low C_obo (10 pF) preserve signal integrity up to 10 kHz without phase shift or roll-off.

DC-DC Converter Feedback

LED Constant-Current Driver

Use Scenario: Used in optocoupler-coupled secondary-side error amplifiers of isolated flyback converters.

IC Role / Device Role / Timing Role: NPN transistor amplifies error signal to drive optocoupler LED, enabling precise output voltage regulation.

Use Value: High h_FE and low V_CE(sat) ensure accurate current transfer ratio and minimal dropout across line/load variations.

Use Scenario: Implements constant-current sink for indicator LEDs in industrial HMI panels.

IC Role / Device Role / Timing Role: Acts as adjustable current sink controlled by DAC or microcontroller GPIO via base resistor.

Use Value: Tight h_FE binning allows predictable current setting with ±5% tolerance using standard 1% resistors.

Microcontroller GPIO Expander

Small-Signal Amplifier Stage

Use Scenario: Drives 12 V relay coils from 3.3 V MCU outputs in programmable logic controllers.

IC Role / Device Role / Timing Role: Level-shifting switch translating low-voltage logic to higher-voltage load control.

Use Value: 45 V V_CEO rating provides margin against inductive kickback; fast turn-off minimizes coil release delay.

Use Scenario: First-stage preamplifier in sensor signal conditioning for pressure transducers.

IC Role / Device Role / Timing Role: Provides voltage gain with low noise and stable bias point in common-emitter configuration.

Use Value: 100 MHz f_T and low C_obo (10 pF) preserve signal integrity up to 10 kHz without phase shift or roll-off.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MMBT3904LT1G	h_FE = 100–300 (at 10 mA); lower I_C rating (200 mA); same SOT-23 package.	Not suitable for 500 mA loads; acceptable only in low-current signal switching or biasing.	Select when design operates below 100 mA and prioritizes cost over current headroom.
BC846B,215	h_FE = 200–450 (at 10 mA); I_C = 100 mA; different gain binning and thermal specs.	Limited to sub-100 mA applications; not validated for continuous 500 mA operation.	Choose for general-purpose low-power amplification where full 500 mA capability is unnecessary.

Compared with MMBT3904LT1G and BC846B,215, the NSCT817-25LT3G uniquely supports 500 mA continuous current with guaranteed h_FE ≥ 160 at that level-making it the only option among the three qualified for high-current switching in space-constrained SOT-23 layouts.

Availability

NSCT817-25LT3G is available at Aetrix Electronics and suitable for DC-DC converter feedback, LED constant-current drivers, microcontroller GPIO expansion, and small-signal amplifier stages requiring stable component supply and Pb-free compliance.

Supply support for NSCT817-25LT3G 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The NSCT817 series belongs to onsemi's general-purpose bipolar transistor product line, designed specifically for cost-sensitive, high-volume applications requiring reliable DC current gain, low saturation voltage, and robust thermal performance in miniature SOT-23 packaging.

FAQ

What is the maximum continuous collector current rating for NSCT817-25LT3G?

The NSCT817-25LT3G is rated for 500 mA continuous collector current (I_C) at T_A = 25°C on FR-5 board. Derating applies above 25°C at 1.8 mW/°C, limiting usable current in high-temperature environments unless thermal management is enhanced. This rating is confirmed in the official onsemi datasheet revision 0 (May 2006).

Does NSCT817-25LT3G have Pb-free construction?

Yes, NSCT817-25LT3G is a Pb-free device compliant with RoHS Directive 2011/65/EU and J-STD-609 Class 3 moisture sensitivity. The "G" suffix in the part number explicitly denotes Pb-free packaging, and the device is qualified for standard lead-free reflow profiles per IPC-J-STD-020.

What is the guaranteed h_FE range for NSCT817-25LT3G at 100 mA collector current?

The NSCT817-25LT3G guarantees h_FE ≥ 160 at I_C = 100 mA and V_CE = 1.0 V, with an upper limit of 400 under those conditions. This binning (−25) is distinct from the −40 variant and ensures predictable base drive requirements in production designs.

Can NSCT817-25LT3G replace MMBT3904LT1G in a 500 mA load circuit?

No-NSCT817-25LT3G supports 500 mA continuous current, while MMBT3904LT1G is rated only for 200 mA. Substituting MMBT3904LT1G in a 500 mA application risks thermal runaway and premature failure. NSCT817-25LT3G is not a drop-in replacement for that current level.

What is the thermal resistance (R_JA) of NSCT817-25LT3G on a standard FR-5 PCB?

The NSCT817-25LT3G has a thermal resistance of R_JA = 556°C/W when mounted on an FR-5 board (1.0 × 0.75 × 0.062 in), per Note 1 in the onsemi datasheet. This value assumes no additional copper pour; adding thermal relief or ground plane reduces effective R_JA in practice.

NSCT817-25LT3G Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

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

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 500 mA

Voltage - Collector Emitter Breakdown (Max):: 45 V

Vce Saturation (Max) @ Ib, Ic:: 700mV @ 50mA, 500mA

Current - Collector Cutoff (Max):: 100nA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 160 @ 100mA, 1V

Power - Max:: 225 mW

Frequency - Transition:: 100MHz

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

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-3 (TO-236)

NSCT817-25LT3G FAQ

1.How can I place an order for NSCT817-25LT3G through Aetrix?

Please submit a Request for Quotation (RFQ) for NSCT817-25LT3G 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 NSCT817-25LT3G reliable?

The price and inventory of NSCT817-25LT3G are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for NSCT817-25LT3G is usually 5 days.

3.What payment methods are accepted for NSCT817-25LT3G?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for NSCT817-25LT3G transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for NSCT817-25LT3G?

NSCT817-25LT3G orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your NSCT817-25LT3G 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 NSCT817-25LT3G?

For technical support, including NSCT817-25LT3G datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your NSCT817-25LT3G requirements.

6.How does Aetrix verify that NSCT817-25LT3G is sourced from the original manufacturer or authorized distributors?

All NSCT817-25LT3G 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 NSCT817-25LT3G meets industry standards.

7.What is the process for return or replacement of NSCT817-25LT3G?

All NSCT817-25LT3G units undergo pre-shipment inspection (PSI). If there is an issue with NSCT817-25LT3G, 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 NSCT817-25LT3G part is unused and in its original packaging.

Return procedure for NSCT817-25LT3G:

1.Submit a request within 90 days.

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

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