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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

onsemi KSA1242YTU

Name: KSA1242YTU
Brand: onsemi
SKU: KSA1242YTU
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: KSA1242YTU

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-251-3 Short Leads, IPAK, TO-251AA

Datasheet:: KSA1242YTU.pdf

Description:: TRANS PNP 20V 5A IPAK

Quantity:: RFQ Add To RFQ list

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Product details

Overview

KSA1242YTU from ON Semiconductor (formerly Fairchild) is a PNP epitaxial silicon power transistor in I-PAK package, rated for -20 V V_CEO, -5 A continuous collector current, and 10 W power dissipation at T_C = 25°C, commonly used in medium-power amplifier stages and camera flash discharge circuits.

For engineers reviewing the KSA1242YTU datasheet, pinout, applications, or equivalent options, key selection criteria include guaranteed h_FE range (160–320 at I_C = -0.5 A), low V_CE(sat) ≤ -1 V at I_C = -4 A / I_B = -0.1 A, f_T = 180 MHz, and I-PAK thermal performance with T_J = 150°C maximum junction temperature.

Technical Context

This PNP bipolar junction transistor operates in linear amplification and switching modes, with DC current gain specified across two test conditions: h_FE1 = 160–320 at V_CE = -2 V, I_C = -0.5 A and h_FE2 ≥ 70 at V_CE = -2 V, I_C = -4 A. Its safe operating area supports pulsed collector currents up to -8 A.

The device features low saturation voltage (-1 V max), high transition frequency (180 MHz), and tight parameter classification (Y-grade h_FE bin), making it suitable for fast-switching, medium-current analog and pulse applications where thermal stability and gain consistency are critical.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	-20 V - Maximum sustainable collector-emitter voltage before breakdown under open-base condition
I_C (DC)	-5 A - Continuous collector current rating defining steady-state conduction capability
P_C	10 W - Power dissipation limit at case temperature 25°C, requiring heatsinking above ambient
h_FE (Y grade)	160–320 - Guaranteed DC current gain range at low-moderate current, enabling predictable bias design
V_CE(sat)	≤ -1 V - Low saturation voltage at I_C = -4 A / I_B = -0.1 A, minimizing conduction loss in switching use
f_T	180 MHz - Transition frequency confirming usable bandwidth for audio and flash-timing signal amplification
C_ob	50 pF - Collector output capacitance at V_CB = -10 V, influencing high-frequency response and switching speed

Pinout & Package

I-PAK package: thermally enhanced surface-mount outline with exposed drain pad (collector-connected), standardized for PCB heat transfer and mechanical robustness in medium-power applications.

Pin/Terminal	Circuit Role	Design Meaning
1 (Base)	Control electrode	Receives base current to regulate collector-emitter conduction; requires current-limiting resistor in driver stage
2 (Collector)	Main current sink	Internally connected to exposed metal tab; must be electrically isolated and thermally coupled to heatsink
3 (Emitter)	Current source reference	Common return path for load current; polarity defines PNP operation (emitter positive relative to collector)

Key Features

Feature	Design Value
Y-grade h_FE binning	Guaranteed h_FE = 160–320 ensures consistent small-signal gain and bias point stability across production lots
Low V_CE(sat)	V_CE(sat) ≤ -1 V at full-rated I_C reduces power loss and self-heating during saturated switching
180 MHz f_T	Supports reliable amplification of audio-band and flash-trigger signals without gain roll-off
I-PAK thermal design	Exposed collector tab enables direct thermal interface to PCB copper or external heatsink, sustaining 10 W at T_C = 25°C

Applications

Audio Power Amplifier Stage	Camera Flash Discharge Circuit
Use Scenario: Medium-power push-pull output stage in portable audio amplifiers driving 4–8 Ω speakers. IC Role / Device Role / Timing Role: PNP complement in Class AB output pair, delivering negative half-cycle current with matched gain and thermal tracking. Use Value: Y-grade h_FE binning and low V_CE(sat) minimize crossover distortion and conduction loss, improving efficiency and THD.	Use Scenario: High-current switch discharging capacitor bank into xenon flash tube within <100 µs. IC Role / Device Role / Timing Role: Fast-saturation PNP switch controlling flash energy release timing and peak current magnitude. Use Value: 180 MHz f_T and -8 A pulse rating support precise flash duration control and repeatable light output intensity.
DC Motor Driver (H-Bridge Low-Side)	Voltage Regulator Pass Element
Use Scenario: Low-side switch in bidirectional 12 V DC motor control for automotive accessories or industrial actuators. IC Role / Device Role / Timing Role: Saturated PNP switch sinking motor current during reverse or braking phases. Use Value: -5 A DC rating and I-PAK thermal performance enable sustained operation without forced cooling in compact enclosures.	Use Scenario: Series pass transistor in adjustable linear regulator supplying stable 5–15 V to analog sensor subsystems. IC Role / Device Role / Timing Role: Current-controlled series element regulating output voltage via base drive feedback loop. Use Value: Tight h_FE spread and low V_CE(sat) improve load regulation accuracy and reduce dropout voltage under full load.

Audio Power Amplifier Stage

Camera Flash Discharge Circuit

Use Scenario: Medium-power push-pull output stage in portable audio amplifiers driving 4–8 Ω speakers.

IC Role / Device Role / Timing Role: PNP complement in Class AB output pair, delivering negative half-cycle current with matched gain and thermal tracking.

Use Value: Y-grade h_FE binning and low V_CE(sat) minimize crossover distortion and conduction loss, improving efficiency and THD.

Use Scenario: High-current switch discharging capacitor bank into xenon flash tube within <100 µs.

IC Role / Device Role / Timing Role: Fast-saturation PNP switch controlling flash energy release timing and peak current magnitude.

Use Value: 180 MHz f_T and -8 A pulse rating support precise flash duration control and repeatable light output intensity.

DC Motor Driver (H-Bridge Low-Side)

Voltage Regulator Pass Element

Use Scenario: Low-side switch in bidirectional 12 V DC motor control for automotive accessories or industrial actuators.

IC Role / Device Role / Timing Role: Saturated PNP switch sinking motor current during reverse or braking phases.

Use Value: -5 A DC rating and I-PAK thermal performance enable sustained operation without forced cooling in compact enclosures.

Use Scenario: Series pass transistor in adjustable linear regulator supplying stable 5–15 V to analog sensor subsystems.

IC Role / Device Role / Timing Role: Current-controlled series element regulating output voltage via base drive feedback loop.

Use Value: Tight h_FE spread and low V_CE(sat) improve load regulation accuracy and reduce dropout voltage under full load.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJD122G	V_CEO = -100 V, I_C = -8 A, h_FE = 30–250 (unbinned), TO-263 package	Higher voltage rating but wider h_FE tolerance; less suitable for precision gain-critical amplifiers	Prefer when higher breakdown margin is required and gain consistency is secondary
SS8550DTU	V_CEO = -25 V, I_C = -1.5 A, SOT-89 package, h_FE = 120–300	Lower current/power capability and smaller package; limited to <3 W dissipation	Choose only for space-constrained, lower-power designs where I-PAK thermal mass is unnecessary

Compared with MJD122G and SS8550DTU, the KSA1242YTU offers optimal balance of guaranteed Y-bin h_FE, -1 V V_CE(sat), and I-PAK thermal handling for 5 A medium-power switching and amplification-neither over-specified nor under-rated for its target applications.

Availability

KSA1242YTU is available at Aetrix Electronics and suitable for audio amplifier modules, camera flash drivers, DC motor controllers, and linear voltage regulators requiring stable component supply and traceable sourcing.

Supply support for KSA1242YTU 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 (acquired Fairchild Semiconductor in 2016) is a global semiconductor supplier focused on energy-efficient electronics, with leadership in power management, analog, and discrete devices.

The KSA1242YTU belongs to Fairchild's legacy medium-power bipolar transistor family, designed specifically for high-fidelity audio amplification and high-reliability pulsed power switching in consumer and industrial equipment.

FAQ

What is the maximum continuous collector current rating for the KSA1242YTU?

The KSA1242YTU has a maximum continuous collector current (I_C) rating of -5 A at T_C = 25°C. This rating assumes proper heatsinking; derating is required above 25°C case temperature per the power derating curve in the datasheet. The KSA1242YTU must not exceed this limit in DC operation to avoid thermal runaway or permanent damage.

Does the KSA1242YTU have a guaranteed h_FE range, and what does the 'Y' suffix indicate?

Yes-the 'Y' in KSA1242YTU denotes the Y-grade h_FE bin, guaranteeing DC current gain between 160 and 320 at V_CE = -2 V and I_C = -0.5 A. This tighter specification enables predictable biasing in amplifier and switching circuits. The KSA1242YTU's h_FE remains ≥70 even at I_C = -4 A, supporting high-current operation without gain collapse.

What is the pin configuration of the KSA1242YTU, and how is the collector terminal connected internally?

The KSA1242YTU uses an I-PAK package with pinout: Pin 1 = Base, Pin 2 = Collector, Pin 3 = Emitter. Critically, the collector is internally bonded to the exposed metal tab on the underside of the package. This tab must be electrically isolated from other circuit nodes and thermally connected to a heatsink or large copper pour to maintain safe junction temperature during operation of the KSA1242YTU.

Can the KSA1242YTU be used in switching applications, and what supports fast turn-on/turn-off?

Yes-the KSA1242YTU is qualified for switching use, supported by its 180 MHz transition frequency (f_T), low V_CE(sat) (≤ -1 V), and 50 pF output capacitance (C_ob). These parameters enable sub-microsecond switching transitions when driven with adequate base current. For reliable switching, the KSA1242YTU requires active base drive (not passive pull-up) and attention to stored charge removal during turn-off.

Is the KSA1242YTU RoHS compliant and halogen-free?

Yes-the KSA1242YTU manufactured by ON Semiconductor meets RoHS Directive 2011/65/EU and is halogen-free per J-STD-709 definition. Lead-free soldering profiles compatible with Pb-free assembly are validated per JEDEC J-STD-020. Compliance documentation for the KSA1242YTU is available through ON Semiconductor's quality portal and distributor certifications.

KSA1242YTU Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-251-3 Short Leads, IPAK, TO-251AA

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: PNP

Current - Collector (Ic) (Max):: 5 A

Voltage - Collector Emitter Breakdown (Max):: 20 V

Vce Saturation (Max) @ Ib, Ic:: 1V @ 100mA, 4A

Current - Collector Cutoff (Max):: 100µA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 160 @ 500mA, 2V

Power - Max:: 10 W

Frequency - Transition:: 180MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: IPAK

KSA1242YTU FAQ

1.How can I place an order for KSA1242YTU through Aetrix?

Please submit a Request for Quotation (RFQ) for KSA1242YTU on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for KSA1242YTU reliable?

The price and inventory of KSA1242YTU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for KSA1242YTU is usually 5 days.

3.What payment methods are accepted for KSA1242YTU?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for KSA1242YTU transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for KSA1242YTU?

KSA1242YTU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your KSA1242YTU order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for KSA1242YTU?

For technical support, including KSA1242YTU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your KSA1242YTU requirements.

6.How does Aetrix verify that KSA1242YTU is sourced from the original manufacturer or authorized distributors?

All KSA1242YTU products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that KSA1242YTU meets industry standards.

7.What is the process for return or replacement of KSA1242YTU?

All KSA1242YTU units undergo pre-shipment inspection (PSI). If there is an issue with KSA1242YTU, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The KSA1242YTU part is unused and in its original packaging.

Return procedure for KSA1242YTU:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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