2N4125 Pinout, Equivalent, Application, Datasheet

The 2N4125 pinout follows the Emitter–Base–Collector (E–B–C) sequence and is widely used as a low-power PNP transistor in signal amplification, switching, and complementary circuit designs. It operates with a collector–emitter voltage (Vce) of 30V, a collector–base voltage (Vcb) of 30V, a maximum collector current of 200mA, and a power dissipation of 650mW. The 2N4125 transistor is the complementary pair of the 2N4123 NPN transistor, making them ideal for push-pull amplifier and balanced driver circuits.

Introduction to 2N4125 PNP Transistor

The 2N4125 PNP transistor is a silicon-based small-signal transistor designed for low-power amplifier and switching applications. It is housed in a TO-92 plastic package, making it suitable for compact and efficient circuit layouts.

With its low noise characteristics, stable gain, and fast switching performance, the 2N4125 transistor is a reliable choice in analog circuits, oscillators, and audio preamplifier stages. Its polarity and characteristics perfectly complement the 2N4123 NPN transistor, enabling the design of symmetrical amplifier circuits and complementary output stages.

2N4125 PNP Transistor

Pinout of 2N4125

Understanding the 2N4125 Pinout Configuration

The 2N4125 pinout is easy to identify for circuit assembly. When viewed from the flat side of the TO-92 package, the pins are arranged as Emitter–Base–Collector (E–B–C).

Pin Configuration of 2N4125 Pinout

Key Features of 2N4125 Transistor

• Small-signal PNP transistor for general-purpose use
• Designed for low-power amplification and switching
• Excellent frequency response for high-speed circuits
• Stable gain and low noise performance
• Compact and reliable TO-92 package
• Complementary to 2N4123 NPN transistor

2N4125 Transistor Datasheet and Specifications

• Collector–Emitter Voltage (Vce): 30V
• Collector–Base Voltage (Vcb): 30V
• Emitter–Base Voltage (Veb): 5V
• Collector Current (Ic): 200mA
• Total Power Dissipation (Pc): 650mW
• DC Current Gain (hFE): 50 to 250
• Transition Frequency (fT): 200MHz (typical)
• Package Type: TO-92
• Polarity Type: PNP
• Pin Configuration: Emitter–Base–Collector (E–B–C)

Working Principle of 2N4125 Transistor

The 2N4125 PNP transistor operates on the principle of current-controlled conduction, where a small base current regulates the larger collector current. When the base is held at a lower potential relative to the emitter, the transistor allows current to flow from emitter to collector.

This property makes the 2N4125 transistor suitable for use as a switch in low-voltage control circuits or as an amplifier in analog signal processing. Due to its fast response time and balanced characteristics, it performs efficiently in audio driver, filter, and oscillator circuits.

More Circuit Layouts

Typical Applications of 2N4125

• Low-noise amplifier and audio signal preamplification
• Switching circuits in analog and digital devices
• Push-pull amplifier stages with 2N4123 NPN
• Oscillator, multivibrator, and modulator circuits
• General-purpose low-voltage switching
• Analog signal processing and waveform shaping

NPN Complementary Transistor

The 2N4123 NPN transistor serves as the complementary device to the 2N4125 PNP transistor. Both share identical voltage, current, and power ratings, making them suitable for balanced amplifier designs and complementary switching circuits.

When used together, the 2N4125–2N4123 pair provides symmetrical operation, improved linearity, and reduced distortion in push-pull amplifier configurations.

Equivalent Transistors and Alternatives

• 2N3906 – General-purpose PNP transistor
• BC558 – Low-noise PNP for amplifier circuits
• PN2907A – Medium current PNP transistor
• 2N4403 – High-gain small-signal PNP transistor
• S9015 – Equivalent small-signal PNP device for low-voltage use

Comparison Summary: 2N4125 vs 2N4123

The 2N4125 (PNP) and 2N4123 (NPN) transistors are complementary pairs with matched electrical characteristics, differing only in polarity. The 2N4125 transistor conducts when its base is more negative than its emitter, while the 2N4123 transistor conducts when its base is more positive.

This complementary relationship allows designers to build push-pull stages, driver circuits, and balanced amplifiers that deliver symmetrical output with minimal distortion. Together, they form an efficient pair for low-power audio and analog applications.

Frequently Asked Questions (FAQ)

What is the maximum collector current of 2N4125?

The maximum collector current (Ic) is 200mA, suitable for small-signal circuits.

Can 2N4125 be used for amplification?

Yes, the 2N4125 transistor is commonly used for audio preamplifiers, signal processing, and oscillator circuits.

What is the 2N4125 pin configuration?

The 2N4125 pinout is Emitter–Base–Collector (E–B–C) when viewed from the flat face of the TO-92 package.

What is the complementary transistor for 2N4125?

The 2N4123 NPN transistor is the complementary pair of the 2N4125 transistor.

What is the power dissipation of 2N4125?

The total power dissipation (Pc) is 650mW, making it suitable for low-power signal circuits.

Conclusion

The 2N4125 PNP transistor is a versatile, low-power component ideal for audio amplifiers, oscillators, and switching circuits. With its 30V collector-emitter rating, 200mA current capacity, and 650mW power dissipation, it provides reliable performance and low noise operation in compact electronic designs.

Paired with the 2N4123 NPN transistor, it forms an efficient complementary transistor pair, perfect for push-pull amplifier stages and symmetrical driver circuits, ensuring excellent signal balance and amplification quality.

Datasheet & Pinout of 2N4125 NPN Transistor

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