onsemi KSB744OSTU

Overview

KSB744OSTU 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, and 10 W collector dissipation at T_C=25°C, optimized for audio frequency power amplifier stages in consumer and industrial linear amplifiers.

For engineers reviewing the KSB744OSTU datasheet, pinout, applications, or equivalent options, this device is selected for medium-power PNP switching and linear amplification where complementary NPN pairing (e.g., KSD794 series), low saturation voltage, and stable h_FE across 20 mA–0.5 A bias range are critical.

Technical Context

This PNP bipolar junction transistor operates with fixed-base drive in Class-A/AB audio output stages and DC-coupled driver circuits. Its h_FE classification (R/O/Y) ensures gain consistency across production lots, and its safe operating area (SOA) supports pulsed operation up to -5 A with ≤10 ms pulse width and 50% duty cycle.

The device features low V_CE(sat) of -0.5 V at I_C = -1.5 A / I_B = -0.15 A and f_T of 45 MHz at V_CE = -5 V / I_C = -0.1 A, enabling reliable performance in mid-frequency power amplification and switching applications up to several hundred kHz.

Key Specifications

Pinout & Package

Package: TO-126 (standard 3-lead plastic power package with metal tab for heatsinking; dimensions per Fairchild Rev. A: 16.10 × 13.06 × 4.2 mm, tab electrically connected to collector).

Key Features

Applications

Equivalent & Alternatives

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

Compared with KSB744OSTU, MJD744 trades package form factor and thermal capacity for SMT assembly, while KSB884 extends voltage rating and DC gain at the cost of frequency response-both require explicit validation against SOA, thermal path, and gain matching in final circuit implementation.

Availability

KSB744OSTU is available at Aetrix Electronics and suitable for audio power amplifiers, DC motor driver stages, linear voltage regulators, and bench power supply drivers requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for KSB744OSTU 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 (formerly Fairchild Semiconductor) is a global semiconductor supplier focused on energy-efficient electronics, with leadership in discrete power devices, analog ICs, and automotive semiconductors.

The KSB744OSTU belongs to Fairchild's legacy audio power transistor family, designed specifically for complementary-symmetry linear amplification and medium-power switching in consumer, industrial, and instrumentation equipment.

FAQ

What is the maximum continuous collector current for KSB744OSTU?

The KSB744OSTU has a maximum continuous collector current (I_C) of -3 A at T_A = 25°C. This rating assumes adequate heatsinking; actual usable current decreases with rising case temperature per the 0.12 W/°C derating curve shown in Figure 8 of the datasheet. For sustained operation above 1 A, thermal design must maintain T_C ≤ 100°C to avoid exceeding the 10 W collector dissipation limit.

Is KSB744OSTU pin-compatible with KSB744A?

Yes, KSB744OSTU and KSB744A share identical TO-126 package, pinout (Emitter–Collector–Base), and mechanical dimensions. The key difference is V_CEO: KSB744OSTU is rated at -45 V, while KSB744A is rated at -60 V. All other electrical parameters-including h_FE, V_CE(sat), and f_T-are identical per the shared datasheet. Substitution is permissible where -45 V rating suffices.

What is the typical h_FE range for KSB744OSTU at I_C = -0.5 A?

At V_CE = -5 V and I_C = -0.5 A, the KSB744OSTU exhibits h_FE2 in the range of 60–120 for R-grade units. This value is confirmed in the "hFE Classification" table and Figure 2 of the datasheet. Designers should use h_FE = 60 (min) for worst-case base drive calculations and verify thermal stability at h_FE = 120 (max) under full-load conditions.

Does KSB744OSTU have a specified avalanche rating?

No, the KSB744OSTU datasheet does not specify an avalanche energy rating (E_AS) or ruggedness test data. It is not characterized for unclamped inductive switching. Designers must implement external clamping (e.g., snubbers or TVS diodes) when using KSB744OSTU in inductive load switching applications to prevent secondary breakdown beyond the SOA limits defined in Figure 6.

Can KSB744OSTU be used in surface-mount designs?

No, KSB744OSTU is packaged exclusively in through-hole TO-126 and is not available in surface-mount variants. For SMT equivalents, consider MJD744 (TO-252) or NSS744 (SOT-89), though both differ in ratings and thermal performance. Any migration requires full revalidation of thermal, SOA, and gain-matching behavior in the target application.