With clear advantages in current handling compared to many small-signal PNP transistors, 2N4403 PNP transistor bridges the gap between low-power signal devices and higher-current switching components. This article will discuss the 2N4403 PNP transistor in detail, covering its overview, types, pinout, specifications, applications, comparisons, advantages, limitations, and practical circuit operation.

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2N4403 Transistor Overview

The 2N4403 PNP Transistor from onsemi is a general-purpose bipolar junction transistor. It is designed for reliable switching and signal amplification. As a PNP device, it conducts current when the base voltage is lower than the emitter, making it suitable for low-side and complementary circuit designs. It is commonly supplied in a compact TO-92 package, ideal for through-hole PCB assembly.

This transistor supports a collector-emitter voltage of up to −40 V and a continuous collector current of −600 mA, allowing it to handle moderate loads with good efficiency. The 2N4403 offers stable DC current gain and fast switching performance. Often used as a complement to the 2N4401 NPN transistor.

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Common 2N4403 Types

There are several types of the 2N4403, but they are electrically the same device. The differences are mainly in package, lead form, and ordering code, not in how the transistor works.

• 2N4403A – Same electrical ratings; often a tighter gain or screening variant (depends on manufacturer)

• 2N4403BU – Bulk-packed version

• 2N4403TA – Tape-and-ammo packaging

• 2N4403TF / 2N4403TFR – Tape-and-reel packaging

• MMBT4403 – Surface-mount (SOT-23) version, electrically equivalent

2N4403 Transistor Pinout Details

Alternatives & Equivalents

2N4403 PNP Transistor Equivalents

• NTE159

• KSA708

• 2SA708

• BC527

• BC528

•KN2907

• KSP2907A

2N4403 PNP Transistor Alternatives

• 2N2907

• 2N2907A

• 2N3906

• 2SA1015

• SS9012

•MPS2907

• PN2907

Technical Specifications

Electrical Characteristics

2N4403 Transistor Features

• PNP bipolar junction transistor (BJT)

• General-purpose switching and amplification

• Silicon semiconductor technology

• Through-hole TO-92 package

• Maximum collector-emitter voltage of 40

• Continuous collector current up to 600 mA

• Low collector-emitter saturation voltage

• Stable DC current gain for reliable performance

• High gain-bandwidth product (200 MHz)

• Suitable for complementary use with 2N4401 NPN transistor

• Wide operating temperature range (−65 °C to +150 °C)

• Compact size for space-efficient PCB designs

Switching Time Equivalent Test Circuit

The switching time equivalent test circuit is used to measure how quickly the 2N4403 transistor turns ON and OFF under controlled, repeatable conditions. The test setup applies fast voltage pulses to the base through a 1.0 kΩ resistor, while the collector is connected to a −30 V supply through a 200 Ω load. A very small shunt capacitance (Cs < 10 pF) is maintained to ensure that the measured timing reflects the transistor’s performance rather than external circuit delays.

In the turn-on time test, the base is driven from 0 V to a positive pulse and then pulled negative. This forward-biases the base–emitter junction, allowing the transistor to quickly enter conduction. The waveform shows how long it takes for the collector voltage to respond, indicating the transistor’s rise time and storage behavior during switching.

In the turn-off time test, a reverse base drive is applied to remove stored charge from the base region. The added diode and bias help speed up charge removal, allowing the transistor to return to the OFF state faster. The resulting waveform shows the fall time and storage delay, which are critical for evaluating high-speed switching performance.

2N4403 Transistor Working in Circuit

2N4403 as a Relay Driver with NPN Pre-Driver

In the first circuit, the 2N4403 PNP transistor is used as a high-side switch to drive a relay coil. An NPN transistor (2N4401) acts as a pre-driver, allowing a low-level input signal to control a higher relay current safely. When the input goes high, the 2N4401 turns on and pulls the base of the 2N4403 low through the resistor network. This forward-biases the PNP transistor, allowing current to flow from the positive supply through the relay coil. The 1N4007 diode protects the transistors from voltage spikes generated when the relay is switched off.

2N4403 as an Audio Output Stage in a Siren Simulator

2N4403 as an Audio Output Stage in a Siren Simulator

In the second diagram, the 2N4403 operates as a power amplification stage in an emergency siren simulator. It works together with a 2N4401 to amplify an oscillating audio signal generated by the RC network and pushbutton trigger. The 2N4403 provides the necessary current gain to drive the speaker, while capacitors shape the siren’s rising and falling tone. Here, the transistor’s role is to supply sufficient output current while maintaining signal integrity for audible sound generation.

2N4403 as a High-Side Switch in an H-Bridge Motor Driver

2N4403 as a High-Side Switch in an H-Bridge Motor Driver

In the third circuit, two 2N4403 PNP transistors are used as the high-side devices of an H-bridge, with 2N4401 NPN transistors on the low side. Controlled by Arduino digital pins, the 2N4403 transistors connect the motor to the positive supply when activated. By selectively turning on opposite transistor pairs, the motor can rotate in either direction. This configuration highlights the 2N4403’s suitability for logic-controlled power switching in low-voltage motor applications.