onsemi KSB744YSTU

Overview

KSB744YSTU from ON Semiconductor (formerly Fairchild) is a PNP epitaxial silicon power transistor in TO-126 package, rated for -45 V V_CEO, -3 A DC collector current, 10 W collector dissipation at T_C=25°C, and 45 MHz f_T, used as audio frequency power amplifier stage in discrete amplifier designs.

For engineers reviewing the KSB744YSTU datasheet, pinout, applications, or equivalent options, key selection criteria include verified V_CEO/V_CBO ratings, h_FE classification bands (R/O/Y), saturation voltage under defined I_C/I_B conditions, safe operating area limits, and complementary pairing with KSD794/KSD794A NPN devices.

Technical Context

This PNP bipolar junction transistor operates in linear amplification mode with DC current gain h_FE ranging 30–320 depending on bias point (e.g., 60–120 at I_C = -0.5 A, V_CE = -5 V), and exhibits V_CE(sat) ≤ -0.5 V at I_C = -1.5 A / I_B = -0.15 A. Its f_T of 45 MHz supports audio-band signal amplification without high-frequency roll-off.

The device features low output capacitance (C_ob = 60 pF at V_CB = -10 V, f = 1 MHz) and thermal design enabling 150°C junction operation, with derated power dissipation above 25°C case temperature per Figure 8. It is explicitly designated as complement to KSD794 series for push-pull audio output stages.

Key Specifications

Pinout & Package

Package: TO-126 molded plastic power package with integral metal tab for heatsink mounting; dimensions per Fairchild Rev. A drawing: 16.10 × 13.06 × 4.2 mm (L×W×H), 3.20 mm mounting hole diameter.

Key Features

Applications

Equivalent & Alternatives

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

Compared with KSB744YSTU, MJD744 offers SMT compatibility at minor RF performance cost, while KSA992 trades power handling for higher voltage and frequency-neither matches the original's combination of TO-126 thermal capability, -45 V rating, and 3 A DC current in audio power roles.

Availability

KSB744YSTU is available at Aetrix Electronics and suitable for audio power amplifiers, discrete linear regulators, and industrial analog signal conditioning requiring stable component supply with consistent h_FE binning and proven thermal reliability.

Supply support for KSB744YSTU 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

ON Semiconductor is a global semiconductor supplier delivering energy-efficient, high-performance silicon solutions for automotive, industrial, cloud computing, and consumer electronics markets.

KSB744YSTU belongs to Fairchild's legacy discrete power transistor family, engineered specifically for high-fidelity audio amplification and linear power regulation where matched PNP/NPN pairs and thermal robustness are critical.

FAQ

What is the maximum continuous collector current rating for KSB744YSTU?

The KSB744YSTU has a maximum continuous collector current (I_C) rating of -3 A at T_A = 25°C. This value assumes adequate heatsinking and derates linearly with increasing case temperature per the power derating curve in the datasheet. At T_C = 100°C, the usable I_C drops to approximately -1.5 A. The KSB744YSTU must not exceed this limit in sustained operation to avoid thermal runaway or junction failure.

Is KSB744YSTU pin-compatible with KSD794A?

No, KSB744YSTU is not pin-compatible with KSD794A-the two are complementary PNP and NPN transistors, respectively, both in TO-126 packages with identical pinout (Emitter-Collector-Base), but they serve opposite polarity roles in circuit design. Their matching is electrical (gain, V_CE(sat), SOA), not mechanical substitution. The KSB744YSTU pin 1 is Emitter, pin 2 is Collector, pin 3 is Base-same as KSD794A-so layout reuse is possible in push-pull layouts, but direct replacement is not functionally valid.

What does the 'Y' suffix in KSB744YSTU indicate?

Per Fairchild documentation, the 'Y' in KSB744YSTU denotes the h_FE2 gain classification bin: 160–320 at I_C = -0.5 A and V_CE = -5 V. This high-gain bin enables reduced base drive requirements and tighter bias control in precision amplifier designs. The 'TU' suffix indicates tape-and-reel packaging for automated assembly; 'S' indicates lead-free (Pb-free) construction compliant with RoHS Directive 2011/65/EU.

Can KSB744YSTU be used in switching applications?

Yes, the KSB744YSTU can be used in medium-speed switching applications such as relay drivers or PWM-controlled power stages, provided switching frequency remains below ~100 kHz and SOA limits are respected. Its 45 MHz f_T and low V_CE(sat) support efficient turn-on, but its minority-carrier BJT structure results in slower turn-off than MOSFETs-base charge removal via reverse drive or Baker clamp is recommended for clean transitions.

What is the safe operating area (SOA) limitation for KSB744YSTU at 100°C case temperature?

At T_C = 100°C, the KSB744YSTU's SOA is bounded by thermal dissipation (derated to ~5 W), secondary breakdown (limited to ~-1.2 A at V_CE = -20 V), and peak pulse current (I_CP = -5 A for PW ≤ 10 ms). The device must avoid simultaneous high V_CE and high I_C beyond the SOA boundary shown in Figure 6 of the datasheet-exceeding it risks localized hot-spot formation and permanent failure.