onsemi 2N4401_D81Z

Overview

2N4401_D81Z from ON Semiconductor is a through-hole NPN bipolar junction transistor designed for general-purpose amplification and switching in medium-power circuits, with 40 V V_CEO, 600 mA I_C, 625 mW P_D, and 250 MHz f_T. It operates across –55 °C to +150 °C and is commonly used in relay drivers, LED drivers, and low-speed digital logic interfaces.

For engineers reviewing the 2N4401_D81Z datasheet, pinout, applications, or equivalent options, key selection criteria include its TO-92 package compatibility, DC current gain (h_FE = 40–300 at I_C = 1–500 mA), saturation voltage (V_CE(sat) = 0.40 V @ 150 mA), thermal resistance (R_θJA = 200 °C/W), and ESD robustness in industrial control signal conditioning.

Technical Context

The 2N4401_D81Z implements a silicon planar epitaxial NPN structure optimized for linear amplification and saturated switching. Its h_FE spans 40–300 across collector currents from 1 mA to 500 mA, supporting both analog gain stages and digital on/off control with predictable V_BE(sat) (0.75–1.20 V) and fast switching (t_d = 15 ns, t_f = 30 ns).

It features low output admittance (h_oe = 1–30 μmhos) and moderate input impedance (h_ie = 1–15 kΩ), enabling stable biasing in common-emitter configurations. The device meets JEDEC TO-92 mechanical standards and is rated for continuous operation up to 150 °C junction temperature with derating above 25 °C.

Key Specifications

Pinout & Package

2N4401_D81Z is housed in a JEDEC-compliant TO-92 plastic package with straight leads (bulk or ammo packaging). Pin identification follows standard TO-92 orientation: viewed from flat side with leads down, left-to-right is Emitter (E), Base (B), Collector (C).

Key Features

Applications

Equivalent & Alternatives

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

Compared with 2N4401_D81Z, the 2N2222A offers higher V_CEO but reduced switching speed and higher saturation loss, while the BC547B trades current capacity and thermal margin for tighter h_FE tolerance-making 2N4401_D81Z the balanced choice for medium-power, wide-temperature, and mixed-signal applications.

Availability

2N4401_D81Z is available at Aetrix Electronics and suitable for relay driver circuits, LED indicator interfaces, digital level shifting, audio preamplifier stages, and industrial sensor signal conditioning requiring stable component supply and long-term manufacturability.

Supply support for 2N4401_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

ON Semiconductor is a global semiconductor manufacturer specializing in energy-efficient power management, analog, sensing, and connectivity solutions for automotive, industrial, and consumer markets.

The 2N4401_D81Z belongs to ON Semiconductor's legacy general-purpose bipolar transistor family, engineered for reliability and consistency in cost-sensitive, high-volume linear and switching applications across diverse environmental conditions.

FAQ

What is the maximum collector-emitter voltage rating for the 2N4401_D81Z?

The 2N4401_D81Z has a maximum collector-emitter voltage (V_CEO) rating of 40 V. This value is specified under test conditions of I_C = 1.0 mA and I_B = 0 at T_A = 25 °C. Exceeding this voltage risks avalanche breakdown and permanent device damage. Designers must maintain at least 20% margin below 40 V in DC-coupled applications and verify transient clamping in inductive switching scenarios.

Is the 2N4401_D81Z suitable for switching a 500 mA load?

Yes, the 2N4401_D81Z supports continuous collector currents up to 600 mA, making it suitable for switching 500 mA loads. However, at I_C = 500 mA, V_CE(sat) rises to 0.75 V and h_FE drops to 40, requiring ≥12.5 mA base drive. Thermal design must account for P_D ≈ 375 mW at saturation, necessitating adequate PCB copper area or ambient derating per the 5.0 mW/°C curve.

What package type does the 2N4401_D81Z use, and how is it oriented?

The 2N4401_D81Z uses a TO-92 plastic package with three leads in straight-line configuration. When viewed from the flat side with leads pointing downward, the pin order left-to-right is Emitter (E), Base (B), Collector (C). This orientation matches JEDEC TO-92 standard drawings and is verified in ON Semiconductor's MMBT4401/D datasheet Figure 1 and physical dimension diagrams.

Does the 2N4401_D81Z have a specified ESD rating?

The 2N4401_D81Z does not list a human-body model (HBM) or charged-device model (CDM) ESD rating in its official ON Semiconductor datasheet. While the TO-92 package provides some inherent protection, designers handling or assembling the 2N4401_D81Z should follow standard ESD precautions-including grounded workstations, ionized air, and static-dissipative packaging-to prevent latent damage during PCB assembly or bench testing.

How does the 2N4401_D81Z compare to the MMBT4401 SOT-23 variant?

The 2N4401_D81Z is the through-hole TO-92 version, while the MMBT4401 is the surface-mount SOT-23 variant. Both share identical electrical specifications (V_CEO, I_C, h_FE, f_T), but differ in thermal performance: the 2N4401_D81Z has R_θJA = 200 °C/W versus 357 °C/W for MMBT4401, and P_D = 625 mW versus 350 mW. The 2N4401_D81Z is preferred for higher-power or prototyping use; MMBT4401 suits compact, automated assembly.