onsemi 2N4400TF

Overview

2N4400TF from Fairchild Semiconductor is an NPN general-purpose bipolar junction transistor (BJT) designed for amplification and switching applications with continuous collector current up to 600 mA, V_CEO = 40 V, and V_CBO = 60 V. It operates across -55°C to +150°C and is commonly used in low-voltage DC-DC converter control stages, relay drivers, and signal buffering circuits.

For engineers reviewing the 2N4400TF datasheet, pinout, applications, or equivalent options, key selection criteria include its guaranteed h_FE ≥ 20 at I_C = 1.0 mA, V_CE(sat) ≤ 0.40 V at I_C = 150 mA / I_B = 15 mA, thermal resistance R_θJA = 200°C/W in TO-92, and suitability for discrete switch/amplifier nodes requiring robust junction temperature margin.

Technical Context

The 2N4400TF is a silicon NPN BJT optimized for linear amplification and saturated switching. Its DC current gain (h_FE) ranges from 20 to 150 depending on operating point, with guaranteed minimum of 20 at I_C = 1.0 mA and 50 at I_C = 150 mA. It supports fast switching with t_d = 15 ns, t_r = 20 ns, t_s = 225 ns, and t_f = 30 ns under specified test conditions.

Thermal design is constrained by R_θJA = 200°C/W (TO-92), limiting power dissipation to 625 mW at T_A = 25°C, derated by 5.0 mW/°C above that ambient. Junction-to-case resistance is 83.3°C/W, indicating suitability for moderate-power discrete stage use without forced cooling.

Key Specifications

Pinout & Package

2N4400TF is packaged in TO-92, a through-hole plastic case with three leads arranged in emitter-base-collector (E-B-C) order when viewed with flat side facing outward and leads pointing down. The package supports manual soldering and board-level mechanical retention.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MMBT4400 and 2N2222A, the 2N4400TF offers superior thermal performance in TO-92 (R_θJA = 200°C/W vs. 357°C/W), lower V_CE(sat) at 150 mA, and faster fall time-making it optimal for thermally demanding, medium-speed switching where through-hole mounting is acceptable.

Availability

2N4400TF is available at Aetrix Electronics and suitable for relay drivers, LED current regulators, signal level shifters, and DC-DC converter switches requiring stable component supply and long-term industrial availability.

Supply support for 2N4400TF 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete devices before its acquisition by ON Semiconductor in 2016.

The 2N4400TF belongs to Fairchild's legacy general-purpose BJT family, engineered for cost-sensitive, high-reliability discrete amplification and switching in industrial control, power supply, and interface circuits.

FAQ

What is the maximum continuous collector current rating for the 2N4400TF?

The 2N4400TF has a maximum continuous collector current (I_C) rating of 600 mA at T_A = 25°C. This value decreases with rising ambient temperature due to thermal derating of 5.0 mW/°C. At 75°C ambient, usable I_C drops to approximately 400 mA assuming V_CE(sat) remains within spec. Always verify junction temperature using R_θJA = 200°C/W in thermal calculations for the 2N4400TF.

Is the 2N4400TF pin-compatible with the MMBT4400?

No-the 2N4400TF uses TO-92 packaging with E-B-C lead order, while the MMBT4400 is in SOT-23 with different pinout (Emitter-Base-Collector mapped to pins 1-2-3). They share identical electrical specifications but differ mechanically and thermally. Substituting the 2N4400TF for MMBT4400 requires PCB redesign and through-hole assembly; the 2N4400TF cannot be mounted on SOT-23 footprints.

What is the typical small-signal current gain (hfe) of the 2N4400TF at 100 MHz?

The 2N4400TF exhibits a typical small-signal current gain (h_fe) of 2.0 at f = 100 MHz, I_C = 20 mA, and V_CE = 10 V. This value reflects its usable bandwidth limit for RF amplification; for audio or low-MHz switching, h_fe rises to 20–250 depending on bias. The 2N4400TF is not intended for high-gain RF stages but performs well in broadband switching and general-purpose amplification up to ~50 MHz.

Does the 2N4400TF support operation at -55°C?

Yes-the 2N4400TF is fully specified from -55°C to +150°C for both operating and storage conditions. Electrical parameters including V_(BR)CEO, h_FE, and V_CE(sat) are characterized across this full range. At -55°C, h_FE decreases slightly but remains functional, and leakage currents (e.g., I_CEX) drop significantly. The 2N4400TF is qualified for extended-temperature industrial and outdoor equipment where cold-start reliability is critical.

What is the base-emitter saturation voltage (V_BE(sat)) of the 2N4400TF at 500 mA collector current?

At I_C = 500 mA and I_B = 50 mA, the 2N4400TF has a maximum V_BE(sat) of 0.95 V, with typical values around 0.85 V. This ensures sufficient forward bias for deep saturation while limiting base drive power dissipation. For designs targeting 500 mA loads, a 10:1 I_B:I_C ratio is recommended, and the 2N4400TF's V_BE(sat) stability supports predictable base resistor sizing across temperature-critical for repeatable switching in the 2N4400TF.