onsemi KSE171STU

Overview

KSE171STU from ON Semiconductor (formerly Fairchild) is a PNP epitaxial silicon transistor designed for low-power audio amplification and high-speed switching applications. It features V_CEO = −60 V, I_C = −3 A, P_C = 12.5 W at T_C = 25°C, h_FE ≥ 30 at I_C = −500 mA, and f_T = 50 MHz - enabling use in Class-B audio output stages and relay drivers.

For engineers reviewing the KSE171STU datasheet, pinout, applications, or equivalent options, key selection criteria include verified PNP polarity, TO-126 package thermal performance, DC current gain linearity across −100 mA to −1.5 A, saturation voltage behavior under forced β = 10, and safe operating area compliance up to 500 µs pulse width.

Technical Context

This device operates as a medium-power PNP bipolar junction transistor with epitaxial base construction for improved frequency response and ruggedness. Its −60 V V_CEO, −80 V V_CBO, and 50 MHz f_T support stable operation in linear amplification and fast-switching topologies where turn-on/off times are critical.

The KSE171STU delivers defined saturation characteristics: V_CE(sat) = −0.9 V at I_C = −1.5 A / I_B = −150 mA and V_BE(sat) = −1.5 V under same conditions, enabling predictable drive requirements in complementary push-pull configurations.

Key Specifications

Pinout & Package

Package: TO-126 - Three-lead plastic power package with metal tab for heatsinking; case temperature monitoring and mechanical mounting via tab screw.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD2955G and KSB1151YTA, the KSE171STU offers optimal balance of TO-126 footprint, −60 V/−3 A rating, and 50 MHz bandwidth - making it ideal for space-constrained audio and switching designs where thermal management and gain-bandwidth trade-offs are critical.

Availability

KSE171STU is available at Aetrix Electronics and suitable for audio amplifier modules, industrial relay interfaces, DC motor controllers, and linear regulator subsystems requiring stable component supply and long-term obsolescence mitigation.

Supply support for KSE171STU 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, power management, and analog solutions for automotive, industrial, and consumer markets.

The KSE171STU belongs to Fairchild's legacy discrete power transistor family, engineered specifically for cost-sensitive, medium-power linear and switching applications where reliability, thermal performance, and gain consistency are essential.

FAQ

What is the maximum continuous collector current rating for KSE171STU?

The KSE171STU has a maximum continuous collector current (I_C) rating of −3 A at case temperature T_C = 25°C. This rating assumes adequate heatsinking; derating applies above 25°C per the 12.5 W power dissipation limit. At T_C = 100°C, the usable I_C drops to approximately −1.8 A. The KSE171STU must be operated within its Safe Operating Area (SOA) curve, especially under pulsed conditions.

Is KSE171STU pin-compatible with other TO-126 PNP transistors like KSE130 or MJE2955?

No, KSE171STU is not pin-compatible with KSE130 (NPN) or MJE2955 (PNP in TO-220). While all three use TO-style packages, KSE171STU uses TO-126 with pinout E-C-B (Emitter–Collector–Base), whereas MJE2955 uses TO-220 with E-B-C ordering. KSE130 is NPN and electrically opposite. Direct substitution requires verification of polarity, pinout, gain, and SOA - the KSE171STU is intended for complementary use with NPN KSE130 in push-pull stages, not as a drop-in replacement.

What is the typical DC current gain (h_FE) of KSE171STU at −500 mA collector current?

The KSE171STU exhibits a minimum h_FE of 30 at V_CE = −1 V and I_C = −500 mA, with a typical value near 100 and maximum up to 250. This gain range supports stable biasing in Class-B audio output stages and ensures sufficient drive margin for base resistors in switching applications. The KSE171STU's h_FE remains usable down to −1.5 A (min 12), enabling predictable operation across its rated current range.

Can KSE171STU be used in high-frequency switching applications above 1 MHz?

Yes - the KSE171STU has an f_T of 50 MHz and documented turn-off time (t_F) under 200 ns at I_C = −1.5 A, supporting reliable operation up to ~20 MHz in optimized circuits. However, its Cob = 50 pF and V_CE(sat) rise at high current require careful gate/base drive design. For >10 MHz switching, the KSE171STU is viable only with low-inductance layout, active base clamping, and load impedance matching - the KSE171STU is not recommended for RF power amplification but well-suited for audio and SMPS auxiliary switches.

Does KSE171STU have built-in protection features such as thermal shutdown or overcurrent limiting?

No, the KSE171STU is a fundamental bipolar junction transistor with no integrated protection circuitry. It relies entirely on external design safeguards: current-limiting base resistors, heatsinking, SOA-aware layout, and external foldback or shutdown circuitry. Its 150°C maximum junction temperature and −65°C to +150°C storage range define absolute limits - sustained operation above 125°C junction temperature risks parametric shift and premature failure. System-level protection must be implemented externally for the KSE171STU.