2N4401 — 40V 600mA General-Purpose NPN BJT (TO-92)

Overview

The 2N4401 (and its surface-mount version MMBT4401) is a general-purpose NPN bipolar junction transistor manufactured by onsemi, Fairchild, STMicroelectronics, and Central Semiconductor. Housed in a through-hole TO-92 package with standard Emitter - Base - Collector (E-B-C) lead configuration, it is widely stocked as the direct step-up upgrade to the standard 2N3904.

While sharing the same pinout, casing, and $40\text{V}$ voltage rating as the 2N3904, the 2N4401 is rated for a continuous collector current of $600\text{ mA}$ (three times greater than the 2N3904's $200\text{mA}$ limit). Featuring a transition frequency ( $f_T$ ) of $250\text{ MHz}$ and low saturation voltage ( $V_{CE(sat)} \le 0.4\text{V}$ at $500\text{mA}$ ), it is the go-to through-hole transistor for driving $5\text{V}/12\text{V}$ mechanical relays, high-intensity LED arrays, piezoelectric buzzers, small DC toy motors, and high-speed saturation switches.

Quick reference


Transistor Type	Higher-Current General-Purpose NPN BJT
Package	TO-92 (3-pin through-hole) / SOT-23 (MMBT4401)
Collector-Emitter Voltage ( $V_{CEO}$ )	$40\text{ V}$ max
Collector-Base Voltage ( $V_{CBO}$ )	$60\text{ V}$ max
Continuous Collector Current ( $I_C$ )	$600\text{ mA}$ max ( $1.0\text{ A}$ pulsed)
DC Current Gain ( $h_{FE}$ )	$100$ to $300$ ( $I_C = 150\text{mA}, V_{CE} = 1.0\text{V}$ ) / $> 40$ at $500\text{mA}$
Transition Frequency ( $f_T$ )	$250\text{ MHz}$ min
Total Power Dissipation ( $P_D$ )	$625\text{ mW}$ ( $T_A = 25^\circ\text{C}$ )
Complementary PNP Pair	2N4403 (40V PNP)
Operating Temp Range	$-55^\circ\text{C}$ to $+150^\circ\text{C}$

Pinout (TO-92 Package - E-B-C Standard)

Looking at the flat front face with leads pointing downward:

text

        ┌─────────┐
        │  TO-92  │
        │ 2N4401  │
        └─┬───┬───┬─┘
          1   2   3
          E   B   C

Pin	Name	Type	Description
1	`EMITTER`	Emitter Terminal	Emitter (Connect to ground or common return / $0\text{ V}$ )
2	`BASE`	Base Terminal	Base control input (Driven with current via series resistor)
3	`COLLECTOR`	Collector Terminal	Collector output (Connected to switched DC load or supply rail)

Specifications

Parameter	Symbol	Min	Typ	Max	Unit	Conditions
Collector-Emitter Breakdown	$V_{(BR)CEO}$	40	—	—	V	$I_C = 1.0\text{mA}, I_B = 0$
Collector-Base Breakdown	$V_{(BR)CBO}$	60	—	—	V	$I_C = 100\ \mu\text{A}, I_E = 0$
Emitter-Base Breakdown	$V_{(BR)EBO}$	6.0	—	—	V	$I_E = 100\ \mu\text{A}, I_C = 0$
DC Current Gain ( $h_{FE}$ )	$h_{FE}$	60	—	—	—	$I_C = 1.0\text{mA}, V_{CE} = 1.0\text{V}$
DC Current Gain ( $h_{FE}$ )	$h_{FE}$	100	—	300	—	$I_C = 150\text{mA}, V_{CE} = 1.0\text{V}$
DC Current Gain ( $h_{FE}$ )	$h_{FE}$	40	—	—	—	$I_C = 500\text{mA}, V_{CE} = 2.0\text{V}$
Collector Saturation Voltage	$V_{CE(sat)}$	—	—	0.40	V	$I_C = 500\text{mA}, I_B = 50\text{mA}$
Base Saturation Voltage	$V_{BE(sat)}$	0.75	—	1.20	V	$I_C = 500\text{mA}, I_B = 50\text{mA}$

Typical Application Circuit: 12V 400mA Solenoid Driver

text

                       +12V DC Supply
                             │
                     [ + Solenoid / Relay Coil - ]
                             │
                             ├───[ 1N4007 Flyback Catch Diode ]────┐
                             │   (Anode to Collector, Cathode to +12V)
                       [Pin 3: COLLECTOR]                          │
                            2N4401                                 │
  MCU GPIO (3.3V / 5V) [Pin 2: BASE]                               │
          │                  │                                     │
          ├───[ 470Ω - 1kΩ ]─┤                                     │
          │                  ├───[ 10kΩ Base Pull-Down Resistor ]──┤
         GND                 │                                     │
                       [Pin 1: EMITTER]                            │
                             │                                     │
                            GND ───────────────────────────────────┴─── Common GND

Comparison: 2N4401 vs 2N3904 vs 2N2222A

Parameter	2N3904	2N4401	2N2222A
Max Current ( $I_C$ )	$200\text{ mA}$	$600\text{ mA}$	$600\text{ mA}$
$V_{CEO}$ Voltage	$40\text{ V}$	$40\text{ V}$	$40\text{ V}$
Gain at 150mA	Drops severely ( $< 30$ )	High ( $100 \dots 300$ )	High ( $100 \dots 300$ )
Transition Freq ( $f_T$ )	$300\text{ MHz}$	$250\text{ MHz}$	$300\text{ MHz}$
Complementary PNP	2N3906	2N4403	2N2907A

Common mistakes

Assuming base resistor for 2N3904 works identically at 500mA: When switching heavy loads ( $300\text{mA} \dots 500\text{mA}$ ), standard $4.7\text{k}\Omega \dots 10\text{k}\Omega$ base resistors will starve the base of current, leaving the transistor in active/linear mode where it dissipates several watts. For a $500\text{mA}$ load, provide at least $30\text{mA} \dots 50\text{mA}$ of base drive ( $R_B \approx 100\ \Omega \dots 220\ \Omega$ ) or use a MOSFET (like 2N7000 or IRLML6344).

Notes

Suffix Guide: 2N4400 is a lower-gain ( $h_{FE} = 40 \dots 120$ ) variant; 2N4401 is the full performance part; MMBT4401 is the SOT-23 surface-mount package.

Interface	Current-Driven Base Junction
Package	TO-92 Plastic (through-hole) / SOT-23 (MMBT4401)