onsemi MPS4124RLRA

Overview

MPS4124RLRA from onsemi is an NPN silicon general-purpose amplifier transistor in TO-92 package, rated for 25 V_CE, 200 mA continuous collector current, and 625 mW power dissipation at 25°C ambient; used in low-power linear amplification, switching, and signal conditioning circuits in consumer audio and industrial control interfaces.

For engineers reviewing the MPS4124RLRA datasheet, pinout, applications, or equivalent options, key selection criteria include h_FE range (120–360 at I_C = 2 mA), f_T = 170 MHz, V_CE(sat) ≤ 0.3 V, C_ob ≤ 4.0 pF, and thermal resistance R_JA = 200 °C/W - all critical for stable small-signal gain and low-distortion operation in compact PCB layouts.

Technical Context

The MPS4124RLRA operates as a medium-speed, medium-gain bipolar junction transistor optimized for DC-coupled and AC-coupled amplification with guaranteed h_FE ≥ 120 at I_C = 2 mA and ≥ 60 at I_C = 50 mA, supporting both Class-A biasing and saturated switching modes. Its f_T of 170 MHz and low output capacitance (C_ob ≤ 4.0 pF) enable stable performance up to VHF frequencies in tuned amplifier stages.

Thermal design is constrained by R_JA = 200 °C/W and R_JC = 83.3 °C/W, requiring careful heatsinking or derating above 25°C ambient; maximum junction temperature is +150°C, with V_(BR)CEO = 25 V ensuring robustness against transient overvoltage in unregulated supply rails.

Key Specifications

Pinout & Package

Package: TO-92 (Case 29-11), straight or bent lead configuration, epoxy-molded plastic body with 3 leads. Standard marking includes "MPS4124" and date code; Pb-free variant identified by "G" suffix (MPS4124RLRAG).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC547B and PN2222A, the MPS4124RLRA offers tighter h_FE lower bound (120 vs. 110), guaranteed f_T minimum (170 MHz), and lower C_ob, making it preferable for noise-sensitive, bandwidth-constrained amplification where consistent gain and stability are prioritized over raw current capacity.

Availability

MPS4124RLRA is available at Aetrix Electronics and suitable for audio pre-amplifier stages, industrial sensor signal conditioning, and DC motor speed control interfaces requiring stable component supply and long-term manufacturability.

Supply support for MPS4124RLRA 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier delivering energy-efficient, high-performance silicon solutions for automotive, industrial, cloud computing, and IoT applications.

The MPS4124RLRA belongs to onsemi's legacy general-purpose bipolar transistor product line, designed for cost-sensitive, reliability-critical linear and switching functions in consumer, industrial, and communications equipment.

FAQ

What is the maximum safe operating voltage for MPS4124RLRA?

The MPS4124RLRA has a guaranteed V_(BR)CEO of 25 V at I_C = 1.0 mA, meaning it can safely block up to 25 V between collector and emitter under open-base conditions. For reliable long-term operation, design margins should limit V_CE to ≤ 20 V in continuous use, especially at elevated temperatures where leakage and thermal runaway risk increase. The MPS4124RLRA datasheet specifies absolute maximum ratings, not recommended operating conditions.

Does MPS4124RLRA support Pb-free soldering processes?

Yes, the MPS4124RLRA is offered in a Pb-free variant designated MPS4124RLRAG, qualified per J-STD-020 moisture sensitivity level 1 and compatible with standard reflow profiles including lead-free SAC305. The base MPS4124RLRA (non-G suffix) is also RoHS-compliant but may contain lead in the die attach; always verify MSL and solder profile compatibility using the official onsemi packaging bulletin BRD8011/D before production use of MPS4124RLRA.

What is the typical noise figure of MPS4124RLRA and at what conditions is it measured?

The MPS4124RLRA has a maximum noise figure (NF) of 5.0 dB, measured at I_C = 100 µA (not 100 A - correction per datasheet erratum), V_CE = 5.0 V, source resistance R_S = 1.0 kΩ, and frequency f = 1.0 kHz. This value reflects its suitability for low-noise pre-amplification; actual NF in circuit depends on bias point, source impedance matching, and layout parasitics. The MPS4124RLRA datasheet confirms this test condition explicitly on page 2.

Can MPS4124RLRA be used in switching power supply feedback loops?

The MPS4124RLRA is not optimized for high-speed switching in SMPS feedback paths due to its 170 MHz f_T and lack of specified switching time parameters (t_on/t_off). While it can function in low-frequency (<100 kHz) error amplifier stages, dedicated op-amps or faster transistors like the MMBT3904 are preferred for stability and bandwidth. The MPS4124RLRA is best applied in linear amplification or moderate-speed digital interfacing, not primary SMPS control loops.

How does the thermal resistance of MPS4124RLRA affect PCB layout decisions?

With R_JA = 200 °C/W, the MPS4124RLRA's junction temperature rises rapidly under load: at 300 mW dissipation, ΔT = 60°C above ambient. To maintain T_J ≤ 125°C at 70°C ambient, keep power below 275 mW or add ≥ 1 cm² of 2-oz copper pour connected to the collector lead. The MPS4124RLRA's TO-92 package relies on lead conduction and board copper - avoid isolated pads and ensure thermal vias if mounting near heat sources.