onsemi KSD1273QYDTU

Overview

KSD1273QYDTU from Fairchild Semiconductor is an NPN epitaxial silicon power transistor in TO-220F package, rated for 60 V V_CEO, 3 A continuous collector current, and 40 W collector dissipation at T_C = 25°C. It delivers high DC current gain (h_FE = 1200–2500, Class O), low V_CE(sat) (1 V @ I_C = 2 A, I_B = 0.05 A), and 30 MHz f_T, targeting audio amplifier output stages and linear power regulation.

For engineers reviewing the KSD1273QYDTU datasheet, pinout, applications, or equivalent options, key selection criteria include its Class O h_FE binning, TO-220F insulated package enabling screw-mount heatsinking without external insulator, and verified safe operating area up to 100 V / 3 A under pulsed conditions.

Technical Context

This transistor operates as a linear amplifying device with fixed NPN polarity and epitaxial base construction, supporting analog signal amplification and DC power switching. Its design emphasizes high-current linearity and thermal stability, evidenced by junction temperature rating of 150°C and derated power dissipation down to 2 W at ambient (T_A = 25°C).

The KSD1273QYDTU exhibits low saturation voltage and high f_T, indicating suitability for medium-frequency audio amplifiers and regulated DC supplies where gain consistency and switching fidelity matter. Its h_FE classification (O) guarantees minimum 1200 gain at I_C = 0.5 A, V_CE = 4 V - a critical parameter for bias stability in Class AB output stages.

Key Specifications

Pinout & Package

Package: TO-220F - Full-Pak insulated plastic package with metal tab electrically isolated from collector; enables direct screw-mounting to heatsink without mica insulator or shoulder washer.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD127G and 2SC5200, the KSD1273QYDTU offers superior h_FE consistency and optimized SOA for linear operation in 60 V-class audio and regulator designs, while maintaining TO-220F mechanical simplicity and thermal performance.

Availability

KSD1273QYDTU is available at Aetrix Electronics and suitable for audio power amplifiers, linear DC voltage regulators, DC motor controllers, and high-current gate driver circuits requiring stable component supply across production lifecycles.

Supply support for KSD1273QYDTU 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 KSD1273QYDTU belongs to Fairchild's legacy high-h_FE power transistor family, designed specifically for linear audio amplification and analog power regulation where gain stability and thermal robustness are critical.

FAQ

What is the h_FE range for KSD1273QYDTU?

The KSD1273QYDTU is binned as Class O, with guaranteed DC current gain (h_FE) of 1200 to 2500 measured at V_CE = 4 V and I_C = 0.5 A. This tight h_FE range ensures consistent biasing and reduced thermal drift in discrete amplifier output stages, making KSD1273QYDTU especially valuable in matched-pair configurations where gain symmetry matters.

Is KSD1273QYDTU compatible with standard TO-220 heatsinks?

Yes - KSD1273QYDTU uses the TO-220F package, which features an electrically insulated metal tab. This allows direct screw-mounting to standard TO-220-compatible heatsinks without additional insulators, simplifying thermal design and improving thermal transfer efficiency compared to non-insulated TO-220 variants. The KSD1273QYDTU datasheet confirms this "Full PAK" construction.

What is the maximum safe operating voltage for KSD1273QYDTU?

The absolute maximum collector-emitter voltage (V_CEO) for KSD1273QYDTU is 60 V, and the collector-base voltage (V_CBO) is 80 V. These ratings define the upper limits for DC and pulsed operation; exceeding them risks avalanche breakdown. For reliable long-term use in linear applications, design margins should keep V_CE ≤ 45 V under peak signal conditions to avoid secondary breakdown, as confirmed by the SOA graph in the KSD1273QYDTU datasheet.

Can KSD1273QYDTU be used in parallel configurations?

Yes - the KSD1273QYDTU's Class O h_FE binning (1200–2500) and low V_CE(sat) (1 V) support stable current sharing in parallel output stages when emitter resistors (0.1–0.22 Ω) are used. Its consistent gain distribution reduces mismatch-induced thermal imbalance, a known failure mode in multi-transistor linear amplifiers. Always verify thermal coupling and individual SOA compliance when paralleling KSD1273QYDTU units.

Does KSD1273QYDTU require a base resistor in typical applications?

Yes - KSD1273QYDTU requires an external base current limiting resistor in all linear and switching applications to prevent excessive base current (I_B max = 1 A) and ensure stable h_FE-driven operation. Typical values range from 100 Ω to 2.2 kΩ depending on drive source and desired I_C; for example, driving 2 A collector current at h_FE = 1500 requires ~1.3 mA base current, achievable with a 3.9 kΩ resistor from a 5 V logic source. This protection is essential for reliable KSD1273QYDTU operation.