onsemi 2N4400_D81Z

Overview

2N4400_D81Z from Fairchild Semiconductor is an NPN general-purpose bipolar junction transistor (BJT) designed for amplification and switching in low-to-medium power circuits, with V_CEO = 40 V, I_C = 600 mA continuous, h_FE = 20–150 at I_C = 1–500 mA, and TO-92 package. It serves in discrete amplifier stages, digital logic interface drivers, and load-switching applications up to 500 mA.

For engineers reviewing the 2N4400_D81Z datasheet, pinout, applications, or equivalent options, key selection criteria include DC current gain linearity across collector current, saturation voltage behavior at high β conditions, thermal resistance (R_θJA = 200 °C/W), and safe operating area under pulsed switching loads.

Technical Context

The 2N4400_D81Z operates as a single NPN BJT with fixed emitter-base and collector-base junction structures optimized for general-purpose linear amplification and saturated switching. Its h_FE varies from 20 at I_C = 500 mA to 150 at I_C = 1 mA, and V_CE(sat) remains ≤0.75 V at I_C = 500 mA / I_B = 50 mA.

Switching performance is characterized by t_d = 15 ns, t_r = 20 ns, t_s = 225 ns, and t_f = 30 ns under V_CC = 30 V, enabling use in medium-speed digital interfaces and PWM-driven loads below 100 kHz.

Key Specifications

Pinout & Package

2N4400_D81Z is housed in a through-hole TO-92 package with standard C-B-E (Collector-Base-Emitter) lead configuration and 0.1" lead pitch. The package supports manual soldering, wave soldering, and board-level mechanical retention via axial leads.

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 2N4400_D81Z offers superior thermal management in TO-92, faster storage time for PWM fidelity, and verified 500 mA switching capability-making it optimal for cost-sensitive, thermally demanding relay and motor control designs.

Availability

2N4400_D81Z is available at Aetrix Electronics and suitable for relay driver circuits, digital level-shifting interfaces, linear audio preamplifiers, and DC motor PWM controllers requiring stable component supply and long-term industrial availability.

Supply support for 2N4400_D81Z 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, acquired by ON Semiconductor in 2016; its legacy product lines remain widely deployed and supported.

The 2N4400_D81Z belongs to Fairchild's general-purpose BJT family, engineered for robustness, manufacturability, and broad compatibility in industrial, consumer, and automotive auxiliary circuits.

FAQ

What is the maximum continuous collector current rating for the 2N4400_D81Z?

The 2N4400_D81Z has an absolute maximum continuous collector current (I_C) of 600 mA at T_A = 25°C. For reliable operation, design should limit I_C to ≤500 mA with appropriate thermal derating above 25°C ambient, per its R_θJA = 200 °C/W specification. Exceeding this without heatsinking risks junction overheating and parametric drift.

Does the 2N4400_D81Z support switching applications, and what are its key timing parameters?

Yes, the 2N4400_D81Z is qualified for switching use with documented t_d = 15 ns, t_r = 20 ns, t_s = 225 ns, and t_f = 30 ns under V_CC = 30 V and I_C = 150 mA. These values confirm suitability for PWM-based motor control and relay driving up to ~100 kHz, provided base drive is sized to achieve full saturation within t_s.

What is the DC current gain (h_FE) range of the 2N4400_D81Z across operating conditions?

The 2N4400_D81Z exhibits h_FE = 20–150 depending on collector current and V_CE: minimum 20 at I_C = 500 mA, 40 at I_C = 10 mA, and up to 150 at I_C = 1 mA. This wide spread requires careful bias network design-especially in linear amplifiers-to maintain stability across temperature and signal amplitude.

Is the 2N4400_D81Z RoHS compliant and halogen-free?

Yes, the 2N4400_D81Z conforms to RoHS Directive 2011/65/EU and is halogen-free per J-STD-709. Its TO-92 package uses lead-free matte tin plating and Pb-free molding compound, meeting industrial compliance requirements for new designs and legacy replacements.

Can the 2N4400_D81Z replace the 2N2222A in existing designs?

The 2N4400_D81Z can substitute for the 2N2222A in many switching applications due to matching V_CEO = 40 V and higher I_C capability, but differences exist: 2N4400_D81Z has lower h_FE at mid-current and faster t_s, making it better for PWM but less ideal for high-gain linear stages. Verify saturation voltage and thermal margin in the target circuit before replacement.