onsemi KSA709GBU

Overview

KSA709GBU from Fairchild Semiconductor is a PNP epitaxial silicon transistor designed for high-voltage amplifier and switching applications, featuring VCBO = −160 V, VCEO = −150 V, IC = −700 mA, PC = 800 mW, and fT = 50 MHz. It operates in linear and saturated modes with hFE ranging 70–400 (depending on grade), and is commonly used in horizontal deflection output stages and high-voltage power supply control circuits.

For engineers reviewing the KSA709GBU datasheet, pinout, applications, or equivalent options, key selection considerations include its −150 V VCEO rating, TO-92 package mechanical compatibility, saturation voltage performance at −200 mA/−20 mA drive, DC current gain classification (O/Y/G), and complementarity to KSC1009 for push-pull designs.

Technical Context

This PNP bipolar junction transistor supports high-voltage operation up to −150 V collector-emitter and −160 V collector-base, enabling use in CRT horizontal deflection, flyback transformer drivers, and industrial relay interface circuits. Its 50 MHz fT and low Cob (10 pF at VCB = −10 V) support stable high-frequency amplification without parasitic oscillation.

The device exhibits defined saturation behavior: VCE(sat) = −0.3 V to −0.4 V and VBE(sat) = −0.9 V to −1.0 V under IC = −200 mA / IB = −20 mA conditions, ensuring predictable turn-on loss in switching applications. Thermal design is supported by TJ(max) = 150 °C and PC = 800 mW at Ta = 25 °C.

Key Specifications

Pinout & Package

Package: TO-92 (standard 3-lead plastic package, lead configuration: Emitter–Base–Collector, pin 1–2–3). Dimensions conform to JEDEC TO-92 outline with body height ≤3.86 mm and lead pitch 1.27 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD2955G and KSA992FBU, the KSA709GBU offers optimal balance of −150 V VCEO, TO-92 form factor, and graded hFE for cost-sensitive, space-constrained high-voltage switching-without over-specifying power or voltage beyond typical CRT and industrial control needs.

Availability

KSA709GBU is available at Aetrix Electronics and suitable for horizontal deflection circuits, flyback converter switches, relay driver interfaces, and high-voltage linear amplifiers requiring stable component supply across long-lifecycle industrial and legacy display equipment programs.

Supply support for KSA709GBU 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 KSA709GBU belongs to Fairchild's legacy high-voltage bipolar transistor family, engineered specifically for CRT deflection, industrial power control, and analog signal conditioning where ruggedness, predictable saturation, and TO-92 compatibility were essential.

FAQ

What is the pin configuration of the KSA709GBU?

The KSA709GBU uses a standard TO-92 package with pin 1 = Emitter, pin 2 = Base, pin 3 = Collector. This configuration is confirmed in Fairchild's Rev. B1 datasheet and matches JEDEC TO-92 mechanical drawings. The KSA709GBU does not use center-collector orientation-the suffix "-C" applies only to other variants in the KSA709 family, not this part.

Is the KSA709GBU a direct replacement for KSA709Y or KSA709O?

Yes-the KSA709GBU is functionally identical to KSA709Y and KSA709O except for hFE grading: G denotes 200–400, Y is 120–240, and O is 70–140. All share identical absolute maximum ratings, electrical characteristics, package, and pinout. The KSA709GBU may be substituted where higher DC current gain is beneficial or required.

What is the maximum safe operating frequency for the KSA709GBU in amplifier mode?

The KSA709GBU has an fT of 50 MHz, but practical small-signal amplifier use is limited to ≤10 MHz due to gain roll-off and stability constraints in common-emitter configurations. At IC = −50 mA and VCE = −10 V, measured gain drops 3 dB near 5–8 MHz; the KSA709GBU is not intended for RF or broadband applications above 15 MHz.

Does the KSA709GBU require a heatsink in switching applications?

For pulsed operation at ≤200 mA IC and ≤50% duty cycle, the KSA709GBU typically operates within its 800 mW PC limit without external heatsinking. However, continuous conduction above 300 mA or ambient temperatures >60 °C necessitates PCB copper pour or minimal heatsinking. Thermal resistance (RθJA) is ~156 °C/W for standard TO-92 mounting; the KSA709GBU's junction temperature must remain ≤150 °C.

How does the KSA709GBU compare to its NPN complement KSC1009?

The KSA709GBU and KSC1009 share matching VCEO (−150 V / +150 V), IC (±700 mA), PC (800 mW), and TO-92 packaging-but opposite polarity and complementary hFE ranges. They are explicitly paired in Fairchild's documentation for push-pull amplifier stages. The KSA709GBU provides symmetrical high-voltage switching capability when used with KSC1009 in Class-B or quasi-complementary output designs.