onsemi 2N4125_S00Z

Overview

2N4125_S00Z from Fairchild Semiconductor is a PNP general-purpose bipolar junction transistor used for low-to-mid current amplification and switching in linear and digital circuits, with V_CEO = 30 V, I_C = 200 mA continuous, h_FE = 50–150 at I_C = 2 mA, and TO-92 package. It serves in signal conditioning stages of sensor interfaces and discrete logic-level translators.

For engineers reviewing the 2N4125_S00Z datasheet, pinout, applications, or equivalent options, key selection criteria include verified PNP polarity, guaranteed V_CEO/V_CBO = 30 V rating, h_FE range across operating currents, thermal resistance (R_θJA = 200 °C/W), and TO-92 mechanical compatibility.

Technical Context

The 2N4125_S00Z operates as a silicon PNP BJT with base-controlled current amplification, supporting both active-mode amplification (e.g., preamplifier stages) and saturated-switching operation (e.g., relay drivers). Its design targets DC and low-frequency AC applications up to ~100 MHz small-signal gain bandwidth.

It features low noise figure (NF = 5.0 dB at 10 Hz–15.7 kHz), moderate input/output capacitance (C_ib = 10 pF, C_ob = 4.5 pF), and specified saturation voltages (V_CE(sat) = 0.4 V, V_BE(sat) = 0.95 V at I_C = 50 mA/I_B = 5 mA), enabling predictable turn-on behavior in switching designs.

Key Specifications

Pinout & Package

2N4125_S00Z is housed in a through-hole TO-92 package with standard PNP lead configuration: Emitter (pin 1), Base (pin 2), Collector (pin 3), viewed from flat side with leads down.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPSA92 and BC557, the 2N4125_S00Z delivers balanced performance for mid-current, low-noise, and thermally constrained applications-offering tighter h_FE control than BC557 and more appropriate voltage rating than MPSA92 for 24 V industrial systems.

Availability

2N4125_S00Z is available at Aetrix Electronics and suitable for industrial sensor interfaces, audio preamplifier stages, and discrete logic-level translation requiring stable component supply and long-term obsolescence management.

Supply support for 2N4125_S00Z 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 before its acquisition by ON Semiconductor in 2016.

The 2N4125_S00Z belongs to Fairchild's legacy general-purpose bipolar transistor family, designed for cost-sensitive, reliability-critical linear and switching functions in industrial and consumer equipment.

FAQ

What is the maximum continuous collector current rating for the 2N4125_S00Z?

The 2N4125_S00Z has a maximum continuous collector current (I_C) rating of 200 mA at T_A = 25°C. This rating must be derated linearly above 25°C ambient temperature at 5.0 mW/°C, per its thermal specification. Operation beyond this limit risks thermal runaway or permanent degradation of the 2N4125_S00Z junction.

Does the 2N4125_S00Z have a specified noise figure, and under what conditions?

Yes, the 2N4125_S00Z has a specified noise figure of 5.0 dB, measured at I_C = 100 µA, V_CE = 5.0 V, R_S = 1.0 kΩ, and frequency range 10 Hz to 15.7 kHz. This value confirms its suitability for low-noise audio preamplifier applications where signal integrity is critical, and is a documented characteristic of the 2N4125_S00Z in its official datasheet.

What is the pin configuration of the 2N4125_S00Z in its TO-92 package?

The 2N4125_S00Z uses standard TO-92 pinout: when viewing the flat side of the package with leads pointing downward, pin 1 is Emitter, pin 2 is Base, and pin 3 is Collector. This configuration is consistent across Fairchild's 2N4125_S00Z production and matches industry-standard PNP TO-92 orientation for reliable PCB layout and assembly.

Can the 2N4125_S00Z be used in switching applications, and what saturation parameters support that?

Yes, the 2N4125_S00Z is qualified for switching use, with V_CE(sat) ≤ 0.4 V and V_BE(sat) ≤ 0.95 V specified at I_C = 50 mA and I_B = 5.0 mA. These values confirm robust saturation behavior, enabling efficient on-state operation in discrete load switches-such as relay drivers-where low conduction loss is essential for the 2N4125_S00Z.

What is the operating junction temperature range for the 2N4125_S00Z?

The 2N4125_S00Z has an operating and storage junction temperature range of –55°C to +150°C, with absolute maximum ratings based on a 150°C junction limit. This wide range supports deployment in harsh environments such as industrial controls or automotive under-hood modules, provided board-level thermal design maintains the 2N4125_S00Z within its R_θJA-defined power envelope.