onsemi MPS6521

Overview

MPS6521 from Fairchild Semiconductor is an NPN general-purpose amplifier transistor rated for 25 V V_CEO, 100 mA continuous collector current, and 625 mW power dissipation in TO-92 package; used in low-power signal amplification and switching circuits in consumer audio preamps and sensor interface stages.

For engineers reviewing the MPS6521 datasheet, pinout, applications, or equivalent options, key selection considerations include DC current gain (h_FE = 150–600), V_CE(sat) ≤ 0.5 V at I_C = 50 mA/I_B = 5 mA, and thermal resistance R_θJA = 200 °C/W - critical for ambient-limited linear-stage designs.

Technical Context

The MPS6521 operates as a silicon NPN bipolar junction transistor optimized for general-purpose linear amplification and low-speed switching. Its h_FE spans 150–600 across I_C = 100 µA to 2.0 mA, with V_CE(sat) tightly specified at 0.5 V under forced β = 10 conditions.

Thermal design is constrained by R_θJA = 200 °C/W and maximum junction temperature of 150 °C; derating begins above 25 °C at 5 mW/°C. The device meets JEDEC TO-92 mechanical standards with defined lead spacing and body dimensions.

Key Specifications

Pinout & Package

Package: TO-92 - standard through-hole plastic package with 1.27 mm lead pitch, 3.60 mm body width, and 14.47 mm overall length; compatible with wave-soldering and manual prototyping.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 2N3904 and BC547, the MPS6521 offers superior h_FE uniformity at low I_C (100 µA) and lower V_CE(sat), making it preferable for precision low-current amplification - though its 25 V V_CEO limit restricts use in higher-voltage rails.

Availability

MPS6521 is available at Aetrix Electronics and suitable for audio preamplifiers, sensor interfaces, discrete level shifters, and low-speed relay drivers requiring stable component supply and long-term obsolescence management.

Supply support for MPS6521 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 manufacturer specializing in power management, analog, and discrete devices before its acquisition by ON Semiconductor in 2016.

The MPS6521 belongs to Fairchild's general-purpose bipolar transistor family designed for cost-sensitive, medium-performance linear and switching applications in consumer and industrial electronics.

FAQ

What is the maximum collector-emitter voltage rating for the MPS6521?

The MPS6521 has a maximum collector-emitter voltage (V_CEO) rating of 25 V at T_A = 25 °C. This rating applies under open-base conditions and must be derated at elevated ambient temperatures per the device's thermal characteristics. Exceeding 25 V risks avalanche breakdown and permanent damage to the MPS6521.

What is the DC current gain (h_FE) range of the MPS6521 and how does it vary with operating conditions?

The MPS6521 exhibits h_FE = 150–300 at V_CE = 10 V and I_C = 100 µA, and h_FE = 300–600 at V_CE = 10 V and I_C = 2.0 mA. This variation reflects typical bipolar transistor behavior: gain increases with collector current up to a point, then declines. Designers must verify bias stability across this full h_FE span when using the MPS6521.

Can the MPS6521 be used in switching applications, and what is its saturation voltage?

Yes, the MPS6521 is suitable for low-speed switching applications. Its collector-emitter saturation voltage (V_CE(sat)) is guaranteed ≤ 0.5 V when I_C = 50 mA and I_B = 5 mA - corresponding to a forced beta (β_forced) of 10. This low saturation voltage minimizes conduction loss and self-heating during on-state operation of the MPS6521.

What is the power dissipation limit of the MPS6521 and how does it change with temperature?

The MPS6521 has a maximum total device dissipation (P_D) of 625 mW at T_A = 25 °C. Above 25 °C, it must be derated linearly at 5 mW/°C, reaching zero dissipation at 150 °C ambient. This derating curve is defined by R_θJA = 200 °C/W and ensures safe junction temperature operation for the MPS6521 in real-world enclosures.

Is the MPS6521 available in surface-mount packages, or only in TO-92?

The MPS6521 is exclusively offered in the through-hole TO-92 package, as confirmed by Fairchild's original datasheet and packaging documentation. No SMT variant (e.g., SOT-23 or SC-59) was released for the MPS6521. Designers requiring surface-mount compatibility must select alternatives such as the MMBT3904 or BC847, not the MPS6521.