onsemi KSA940H1TU

Overview

KSA940H1TU from onsemi is a PNP epitaxial silicon power transistor designed for vertical deflection output amplification in CRT display systems, with −150 V V_CEO, −1.5 A I_C, 25 W P_C (T_C=25°C), h_FE of 40–140 at −500 mA, and TO-220-3LD package. It serves as the complementary device to KSC2073 in push-pull horizontal/vertical deflection stages.

For engineers reviewing the KSA940H1TU datasheet, pinout, applications, or equivalent options, key selection criteria include safe operating area (SOA) compliance at pulse loads, V_CE(sat) ≤ −1.5 V under −500 mA/−50 mA drive, thermal derating above 25°C case temperature, and Pb-free TO-220-3LD mechanical compatibility with heatsink mounting.

Technical Context

This PNP power transistor operates in linear amplification mode for vertical scan output stages, requiring precise base current control (I_B up to −0.5 A) and robust SOA handling across DC, 10 ms, and 100 ms pulse conditions. Its f_T of 4 MHz supports stable gain in low-frequency deflection waveforms without high-frequency oscillation risk.

The device features low Cob of 55 pF at −10 V V_CB, minimizing Miller effect distortion in switching transitions, and V_BE(on) of −0.65 to −0.85 V ensures predictable turn-on threshold under varying junction temperatures up to 150°C.

Key Specifications

Pinout & Package

Package: TO-220-3LD (Case 340AT), Pb-free, through-hole mountable with integral metal tab for heatsink attachment. Pin 1 = Base, Pin 2 = Collector (tab-connected), Pin 3 = Emitter.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD2955G and 2SA1943, the KSA940H1TU delivers optimal balance of −150 V rating, 25 W dissipation, and SOA-limited pulse capability specifically for CRT vertical deflection-neither under-specified nor over-engineered for that use case.

Availability

KSA940H1TU is available at Aetrix Electronics and suitable for CRT repair, legacy display system maintenance, industrial analog signal conditioning, and vertical deflection circuit redesign requiring stable component supply and long-term obsolescence mitigation.

Supply support for KSA940H1TU 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

onsemi (formerly ON Semiconductor) is a global semiconductor manufacturer specializing in power management, analog, sensor, and logic devices for automotive, industrial, and consumer applications.

The KSA940H1TU belongs to onsemi's legacy high-voltage bipolar power transistor product line, engineered specifically for reliability-critical analog video deflection and power switching applications in CRT-based systems.

FAQ

What is the maximum safe collector-emitter voltage for KSA940H1TU in continuous operation?

The KSA940H1TU has a V_CEO rating of −150 V at T_C = 25°C. This is the absolute maximum DC voltage it can sustain between collector and emitter without breakdown. Operation above this value-even momentarily-risks permanent damage. Derating is required above 25°C case temperature per the published power derating curve in the datasheet. The KSA940H1TU must never be subjected to flyback transients exceeding −150 V without external clamping.

Is KSA940H1TU pin-compatible with KSC2073 for push-pull designs?

No, KSA940H1TU and KSC2073 are complementary NPN/PNP devices but not pin-compatible. KSA940H1TU uses TO-220-3LD with Pin 1=Base, Pin 2=Collector, Pin 3=Emitter; KSC2073 uses identical package but reversed pinout (Pin 1=Emitter, Pin 2=Collector, Pin 3=Base). PCB layout must account for this inversion. The KSA940H1TU datasheet explicitly states it is the functional complement-not pin-for-pin replacement-for KSC2073.

Does KSA940H1TU require a heatsink in typical CRT vertical output applications?

Yes, the KSA940H1TU requires a properly sized heatsink in all operational modes. Its 25 W P_C rating applies only at T_C = 25°C; real-world case temperatures in enclosed CRT chassis often exceed 60°C, reducing allowable dissipation significantly. Without heatsinking, junction temperature will exceed 150°C under load. Mounting the KSA940H1TU's metal tab to an aluminum heatsink using thermal compound and insulating washer is mandatory for reliability.

What is the typical base-emitter on voltage for KSA940H1TU at rated current?

The KSA940H1TU exhibits a V_BE(on) of −0.65 V to −0.85 V at V_CE = −10 V and I_C = −500 mA, per the datasheet's Electrical Characteristics table. This range reflects production variation and temperature dependence. At higher currents or elevated junction temperatures, V_BE(on) decreases slightly. Designers should use −0.75 V as a nominal value for base resistor calculations, verifying worst-case bias under minimum h_FE (40) and maximum V_BE(on) (−0.85 V) to ensure saturation.

Can KSA940H1TU be used in modern LCD or LED display power supplies?

The KSA940H1TU is not recommended for modern LCD/LED display power supplies. Its −150 V rating and SOA profile are optimized for CRT flyback waveforms, not the high-frequency PWM and synchronous rectification used in contemporary switch-mode power supplies. Newer alternatives offer superior efficiency, integrated protection, and smaller footprints. The KSA940H1TU remains appropriate only for CRT repair, legacy system maintenance, or niche analog amplifier designs where its specific SOA and voltage characteristics are required.