onsemi KSC2688OS

Overview

KSC2688OS from ON Semiconductor (formerly Fairchild) is an NPN epitaxial silicon transistor designed for high-voltage video output stages in color TV systems, featuring V_CEO = 300 V, I_C = 200 mA, P_C = 10 W at T_C = 25°C, and f_T = 50–80 MHz. It operates in linear amplification mode with h_FE ranging 40–250 depending on grade.

For engineers reviewing the KSC2688OS datasheet, pinout, applications, or equivalent options, key selection criteria include high-voltage breakdown capability (300 V), TO-126 thermal performance, chroma/video signal linearity, and DC current gain classification per R/O/Y/G binning.

Technical Context

The KSC2688OS is a discrete high-voltage NPN bipolar junction transistor optimized for analog video output driver circuits where stable gain and low distortion under high collector-emitter voltage are required. Its structure supports operation up to 300 V V_CEO with controlled saturation voltage (V_CE(sat) ≤ 1.5 V at I_C = 50 mA, I_B = 5 mA) and low feedback capacitance (C_re = 3 pF at V_CB = 30 V).

Thermal design relies on case-mounted heatsinking: maximum power dissipation drops linearly from 10 W at T_C = 25°C to zero at T_C = 175°C. Junction temperature is rated to 150°C, and storage range spans –55°C to +150°C - consistent with industrial-grade TV chassis environments.

Key Specifications

Pinout & Package

Package: TO-126 - Molded plastic power package with metal tab for mechanical mounting and thermal conduction to heatsink. Dimensions conform to JEDEC TO-126 standard (16.10 × 13.06 mm body, 3.20 mm lead diameter).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage NPN transistor applications.

Compared with KSC2688OS, the 2SC4027 offers reduced power handling but tighter f_T consistency, while the KSC2690 extends voltage margin at slight bandwidth cost - both retain TO-126 fit and function for service replacement or design refresh.

Availability

KSC2688OS is available at Aetrix Electronics and suitable for color TV repair, analog video equipment refurbishment, and legacy broadcast hardware maintenance requiring stable component supply and long-term traceability.

Supply support for KSC2688OS 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.

The KSC2688OS belongs to Fairchild's legacy high-voltage analog transistor family, engineered specifically for CRT-based video output stages where reliability under sustained high-voltage stress was critical.

FAQ

What is the maximum collector-emitter voltage rating for the KSC2688OS?

The KSC2688OS has a maximum collector-emitter voltage (V_CEO) rating of 300 V at T_C = 25°C. This rating is verified under specified test conditions (I_C = 5 mA, I_B = 0) and defines the upper limit for safe DC or pulse operation in video output circuits. Exceeding this voltage risks avalanche breakdown and permanent device failure. The KSC2688OS must be used within this limit in all designs.

Is the KSC2688OS pin-compatible with other TO-126 NPN transistors like the 2SC2073?

No, the KSC2688OS is not pin-compatible with the 2SC2073. While both use TO-126 packages, the 2SC2073 has pinout E-C-B (Emitter–Collector–Base), whereas the KSC2688OS uses E-C-B ordering confirmed in its datasheet: Pin 1 = Emitter, Pin 2 = Collector, Pin 3 = Base. Swapping them without verifying pin mapping may cause circuit malfunction or damage. Always confirm pinout before substitution.

What does the 'OS' suffix in KSC2688OS indicate?

Within Fairchild's historical part numbering, the 'OS' suffix in KSC2688OS denotes a specific manufacturing lot or screening variant - often indicating enhanced reliability testing or tighter parameter binning (e.g., guaranteed h_FE ≥ 100). It does not change electrical specifications or package, but reflects traceable production compliance for service and repair channels. The KSC2688OS retains all base KSC2688 specs including V_CEO = 300 V and f_T = 50–80 MHz.

Can the KSC2688OS be used in switching power supply applications?

The KSC2688OS is not optimized for high-frequency switching power supplies. Its f_T of 50–80 MHz and relatively high V_CE(sat) (≤1.5 V) make it less efficient than modern MOSFETs or RF-optimized BJTs in SMPS topologies. It was designed for linear video amplification, not hard-switching. Using KSC2688OS in switch-mode converters may result in excessive conduction loss and thermal runaway. Use only in linear or quasi-linear roles as intended.

How is thermal management handled for the KSC2688OS in continuous operation?

The KSC2688OS requires mechanical mounting of its metal tab to an external heatsink to sustain its 10 W collector dissipation rating at T_C = 25°C. Power derating is linear: above 25°C case temperature, allowable P_C decreases by ~67 mW/°C until reaching zero at 175°C. PCB copper area alone is insufficient; forced-air or conductive heatsinking is mandatory for continuous video output loads. Thermal design must reference the KSC2688OS package dimensions and mounting torque limits.