onsemi NSCT3904LT1G

Overview

NSCT3904LT1G from onsemi is an NPN silicon general-purpose transistor in SOT-23 package, rated for V_CEO = 40 V, I_C = 200 mA, and f_T = 300 MHz, with h_FE = 100–300 at I_C = 10 mA, used in low-voltage switching and small-signal amplification circuits.

For engineers reviewing the NSCT3904LT1G datasheet, pinout, applications, or equivalent options, key selection factors include its Pb-free SOT-23 footprint, guaranteed V_CE(sat) ≤ 0.2 V at I_C/I_B = 10, C_obo ≤ 4.0 pF, and thermal resistance R_JA = 556 °C/W on FR-5 board.

Technical Context

This device operates as a discrete NPN bipolar junction transistor optimized for general-purpose linear amplification and digital switching. Its h_FE variation across I_C (40–300) and low V_BE(sat) (0.65–0.85 V) support stable biasing in emitter-follower and common-emitter configurations.

Designed for surface-mount use on standard PCBs, it delivers predictable small-signal gain (h_fe = 100–400) and noise figure ≤ 5.0 dB at 1 kHz with 100 µA collector current, while maintaining tight C_ibo ≤ 8.0 pF and output admittance h_oe ≤ 40 µmhos.

Key Specifications

Pinout & Package

SOT-23 (Case 318, Style 6) surface-mount plastic package with 1.0 mm × 1.4 mm footprint, 0.95 mm height, and gull-wing leads; designed for reflow soldering on FR-5 or alumina substrates.

Key Features

Applications

Equivalent & Alternatives

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

Compared with NSCT3904LT1G, MMBT3904LT1G offers identical performance with alternate packaging, while BC846B,215 trades higher guaranteed h_FE for slightly elevated saturation voltage-making it better suited for analog bias stability but less optimal for ultra-low-loss switching.

Availability

NSCT3904LT1G is available at Aetrix Electronics and suitable for audio preamplifiers, logic-level switch drivers, and DC-DC converter feedback circuits requiring stable component supply, consistent parametric performance, and RoHS-compliant manufacturing.

Supply support for NSCT3904LT1G 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 specializing in energy-efficient power management, analog, sensors, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The NSCT3904LT1G belongs to onsemi's general-purpose bipolar transistor product line, engineered for cost-sensitive, high-volume applications where reliability, Pb-free compliance, and standardized SOT-23 compatibility are essential.

FAQ

What is the maximum continuous collector current rating for NSCT3904LT1G?

The NSCT3904LT1G has a maximum continuous collector current (I_C) rating of 200 mA at T_A = 25°C on FR-5 board. Derating applies above 25°C at 1.8 mW/°C, meaning usable current drops to ~150 mA at 85°C ambient. This rating assumes proper PCB copper area and no localized heating from adjacent components. The NSCT3904LT1G must not be operated beyond this limit to avoid thermal runaway or permanent degradation.

Does NSCT3904LT1G support operation in automotive under-hood environments?

Yes, the NSCT3904LT1G supports junction temperatures from −55°C to +150°C, meeting extended temperature requirements for non-safety-critical automotive under-hood applications such as cabin lighting control or HVAC fan drivers. However, it is not AEC-Q101 qualified, so system-level validation-including life testing and board-level thermal profiling-is required before deployment in production vehicles. The NSCT3904LT1G's Pb-free SOT-23 package also complies with automotive soldering standards.

What is the guaranteed h_FE range for NSCT3904LT1G at I_C = 100 mA?

At I_C = 100 mA and V_CE = 1.0 V, the NSCT3904LT1G guarantees h_FE ≥ 30, per the "ON CHARACTERISTICS" table in the official datasheet. This lower gain reflects reduced charge carrier injection efficiency at high current density and informs base drive sizing-e.g., 3 mA base current is needed to sustain 100 mA collector current in saturation. The NSCT3904LT1G's h_FE degrades predictably with increasing I_C, as shown in Figure 15.

Can NSCT3904LT1G replace PN2222A in existing SOT-23 designs?

No-NSCT3904LT1G is not a drop-in replacement for PN2222A because the latter is typically supplied in TO-92 or SOT-23 variants with different pinouts (E-B-C vs B-E-C) and higher V_CEO (60 V). While both are NPN transistors, the NSCT3904LT1G uses SOT-23 Style 6 pinout (Base–Emitter–Collector), whereas many PN2222A SOT-23 versions use Style 1 (Emitter–Base–Collector). Using NSCT3904LT1G without verifying pin alignment risks circuit malfunction. Always confirm pin mapping before substitution.

Is NSCT3904LT1G suitable for RF amplifier stages above 100 MHz?

The NSCT3904LT1G has a minimum f_T of 300 MHz, making it technically capable of amplifying signals up to ~100 MHz with usable gain, but it lacks specified S-parameters, stability factor (K), or matching network recommendations for RF design. Its C_obo ≤ 4.0 pF and C_ibo ≤ 8.0 pF help limit Miller effect, yet layout parasitics dominate performance above 50 MHz. For production RF amplifiers, dedicated RF transistors with documented gain flatness and noise figure vs. frequency are preferred over the NSCT3904LT1G.