onsemi 2N4123TF

Overview

2N4123TF from Fairchild Semiconductor is an NPN general-purpose bipolar junction transistor (BJT) designed for low-to-medium current amplification and switching applications up to 100 mA collector current. It features a V_CEO of 30 V, V_CBO of 40 V, and h_FE ranging from 50 to 150 at I_C = 2.0 mA, operating across –55°C to +150°C. It is commonly used in signal amplification stages, discrete logic interfaces, and low-power relay drivers.

For engineers reviewing the 2N4123TF datasheet, pinout, applications, or equivalent options, key selection considerations include its TO-92 package compatibility, DC current gain consistency at 2–50 mA bias points, saturation voltage performance under 5 mA base drive, thermal resistance (R_θJA = 200°C/W), and noise figure of 6.0 dB at 100 µA/1 kHz.

Technical Context

The 2N4123TF operates as a silicon NPN BJT with fixed-emitter configuration and grounded-base or common-emitter topology support. Its f_T of 250 MHz enables use in audio-frequency amplifiers and low-speed digital switching, while its Cob of 4.0 pF and Cib of 8.0 pF define high-frequency input/output impedance behavior.

Thermal design relies on its R_θJC of 83.3°C/W and maximum power dissipation of 625 mW at 25°C (derated 5.0 mW/°C above ambient), making it suitable for non-heat-sinked PCB-level implementations where junction temperature must remain ≤150°C.

Key Specifications

Pinout & Package

2N4123TF is housed in a through-hole TO-92 package with standard three-terminal configuration: emitter, base, and collector arranged in linear order (E-B-C) when viewed with flat side facing outward and leads downward.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PN2222A and BC547B, the 2N4123TF offers tighter h_FE control at mid-currents (2–50 mA), lower noise, and guaranteed TO-92 E-B-C pinout-making it preferable for cost-sensitive, noise-aware, or layout-constrained designs where 30 V headroom suffices.

Availability

2N4123TF is available at Aetrix Electronics and suitable for audio pre-amplification, discrete logic level translation, and low-power relay driving requiring stable component supply and long-term industrial availability.

Supply support for 2N4123TF 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 components before its acquisition by ON Semiconductor in 2016.

The 2N4123TF belongs to Fairchild's legacy general-purpose BJT family, engineered for reliability and consistency in cost-sensitive analog and switching applications across consumer, industrial, and communications equipment.

FAQ

What is the maximum collector current rating for the 2N4123TF?

The 2N4123TF has a continuous collector current rating (I_C) of 200 mA per its absolute maximum ratings. However, the device is characterized for general-purpose amplifier and switch operation up to 100 mA - this reflects its optimized performance envelope for linearity, gain stability, and thermal management in typical applications. Exceeding 100 mA may require careful thermal derating and verification of V_CE(sat) and h_FE behavior per the datasheet curves.

Is the 2N4123TF RoHS compliant?

Yes, the 2N4123TF is RoHS compliant and lead-free, consistent with Fairchild's transition to green packaging standards prior to its acquisition. The TO-92 package uses matte tin plating on leads, and the device meets JEDEC J-STD-609 Category 1 marking requirements. Full compliance documentation is available via Aetrix Electronics' material declaration portal using the 2N4123TF part number.

Does the 2N4123TF have a documented PSpice or SPICE model?

A verified PSpice model for the 2N4123TF is available from ON Semiconductor's legacy Fairchild component library, referenced as "2N4123" (no 'TF' suffix). The model includes temperature-dependent parameters, junction capacitances (Cob, Cib), and forward/reverse Gummel-Poon characteristics validated against the original 2N4123TF electrical test data. It can be directly instantiated in OrCAD PSpice or LTspice using the manufacturer-provided .lib file.

What is the pinout configuration of the 2N4123TF in the TO-92 package?

The 2N4123TF uses the standard TO-92 E-B-C (Emitter-Base-Collector) pinout: when viewing the flat side of the package with leads pointing downward, the leftmost pin is the emitter, center is base, and rightmost is collector. This matches the JEDEC TO-92 variant 1A configuration and is identical to the 2N2222A pinout - enabling direct footprint reuse where voltage/current specs align.

Can the 2N4123TF replace the 2N3904 in existing designs?

The 2N4123TF is not a direct replacement for the 2N3904 due to key differences: the 2N4123TF has higher V_CEO (30 V vs. 40 V), lower h_FE minimum (50 vs. 100), and higher V_CE(sat) (0.3 V vs. 0.2 V at comparable conditions). While both are TO-92 NPN BJTs, substituting 2N4123TF for 2N3904 may reduce gain margin and increase conduction loss - validation of bias point stability and thermal rise is required before deployment in 2N3904-based 2N4123TF designs.