Send an Inquiry

To receive a quote for your project, please fill in the following information, and we’ll get back to you promptly.

Submit Inventory List

Please fill in the following information, and we’ll get back to you promptly.

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

onsemi KSA1241YTU

Name: KSA1241YTU
Brand: onsemi
SKU: KSA1241YTU
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: KSA1241YTU

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: KSA1241YTU.pdf

Description:: TRANS PNP 50V 2A IPAK

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:2,481

Please send an inquiry. Send us your inquiry, and we will respond immediately.

Product details

Overview

KSA1241YTU from Fairchild Semiconductor is a PNP epitaxial silicon transistor designed for power amplifier and switching applications, featuring V_CEO = −50 V, I_C = −2 A, P_C(T_C=25°C) = 10 W, h_FE = 120–240 (Y-class), and low V_CE(sat) = −0.5 V at I_C = −1 A. It serves as a complementary device to KSC3076 in audio and motor drive output stages.

For engineers reviewing the KSA1241YTU datasheet, pinout, applications, or equivalent options, key selection criteria include its I_C rating, saturation voltage under high-current switching, thermal performance in I-Pak package, and h_FE classification for consistent gain matching in push-pull configurations.

Technical Context

The KSA1241YTU operates as a medium-power PNP bipolar junction transistor with fixed-emitter biasing capability, optimized for linear amplification and hard-switching duty. Its −50 V V_CEO and −55 V V_CBO support operation in split-rail amplifier supplies up to ±30 V.

Designed for use in Class AB audio output stages and DC-DC converter switching circuits, it delivers f_T = 100 MHz and t_ON/t_F = 0.1 µs, enabling stable operation at audio frequencies and fast transient response in PWM-driven loads.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	−50 V - Maximum safe collector-emitter voltage before breakdown in common-emitter configuration
I_C	−2 A - Continuous collector current rating defining maximum load-handling capacity
P_C (T_C=25°C)	10 W - Thermal power dissipation limit when mounted on heatsink at case temperature 25°C
h_FE (Y-class)	120–240 - Guaranteed DC current gain range at V_CE = −2 V, I_C = −1.5 A for matched pair design
V_CE(sat)	−0.5 V - Low saturation voltage at I_C = −1 A, I_B = −0.05 A, minimizing conduction loss
f_T	100 MHz - Transition frequency confirming usable bandwidth up to mid-VHF range
t_ON/t_F	0.1 µs - Fast switching times supporting PWM frequencies above 1 MHz in discrete converters

Pinout & Package

Package: I-Pak (TO-251AA), surface-mount with isolated tab, 3-pin single-ended leadframe. Dimensions: 9.30 × 16.10 × 2.30 mm (L×W×H), tab electrically connected to collector.

Pin/Terminal	Circuit Role	Design Meaning
1 (Base)	Current-controlled input terminal	Receives base drive current to regulate collector current; requires external current-limiting resistor in most switch applications
2 (Collector)	Main current-carrying output terminal	Connected to heatsink via isolated metal tab; carries full load current and dissipates majority of heat
3 (Emitter)	Reference terminal for emitter-follower or common-base operation	Typically tied to supply rail in high-side switch; provides return path for base and collector currents

Key Features

Feature	Design Value
Low V_CE(sat)	−0.5 V at I_C = −1 A enables <1 W conduction loss in 5 W amplifier output stage
High h_FE Y-class	120–240 gain range ensures predictable base drive requirements and reduces driver-stage loading
100 MHz f_T	Supports stable small-signal amplification up to 20 MHz and clean square-wave switching at 1–5 MHz
I-Pak thermal performance	10 W P_C at T_C = 25°C allows direct mounting to PCB copper pour or compact heatsink without thermal derating

Applications

Audio Power Amplifier	DC Motor Driver Stage
Use Scenario: Output push-pull pair in Class AB audio amplifier delivering 5–10 W into 4–8 Ω speaker load. IC Role / Device Role / Timing Role: PNP complement to NPN KSC3076 in quasi-complementary output stage; handles negative half-cycle current. Use Value: Low V_CE(sat) minimizes crossover distortion and thermal imbalance versus NPN partner.	Use Scenario: High-side switch in H-bridge or single-direction DC motor control with 24 V supply. IC Role / Device Role / Timing Role: PNP power switch controlling motor current flow from positive rail to load. Use Value: −2 A I_C rating supports peak motor stall currents; fast t_ON/t_F enables precise PWM speed control.
Linear Voltage Regulator Pass Element	Switch-Mode Power Supply Switch
Use Scenario: Series pass transistor in adjustable 3–15 V, 1.5 A linear regulator with foldback protection. IC Role / Device Role / Timing Role: Adjustable current source regulating output voltage via feedback-controlled base bias. Use Value: High h_FE reduces base drive current burden on error amplifier; 150 °C T_J supports sustained thermal stress.	Use Scenario: Primary-side switch in offline flyback converter operating at 65 kHz with 265 VAC input. IC Role / Device Role / Timing Role: Hard-switched PNP transistor replacing MOSFET where gate drive simplicity is prioritized over efficiency. Use Value: −50 V V_CEO meets 2× input-referred voltage margin; Cob = 40 pF limits capacitive switching loss.

Audio Power Amplifier

DC Motor Driver Stage

Use Scenario: Output push-pull pair in Class AB audio amplifier delivering 5–10 W into 4–8 Ω speaker load.

IC Role / Device Role / Timing Role: PNP complement to NPN KSC3076 in quasi-complementary output stage; handles negative half-cycle current.

Use Value: Low V_CE(sat) minimizes crossover distortion and thermal imbalance versus NPN partner.

Use Scenario: High-side switch in H-bridge or single-direction DC motor control with 24 V supply.

IC Role / Device Role / Timing Role: PNP power switch controlling motor current flow from positive rail to load.

Use Value: −2 A I_C rating supports peak motor stall currents; fast t_ON/t_F enables precise PWM speed control.

Linear Voltage Regulator Pass Element

Switch-Mode Power Supply Switch

Use Scenario: Series pass transistor in adjustable 3–15 V, 1.5 A linear regulator with foldback protection.

IC Role / Device Role / Timing Role: Adjustable current source regulating output voltage via feedback-controlled base bias.

Use Value: High h_FE reduces base drive current burden on error amplifier; 150 °C T_J supports sustained thermal stress.

Use Scenario: Primary-side switch in offline flyback converter operating at 65 kHz with 265 VAC input.

IC Role / Device Role / Timing Role: Hard-switched PNP transistor replacing MOSFET where gate drive simplicity is prioritized over efficiency.

Use Value: −50 V V_CEO meets 2× input-referred voltage margin; Cob = 40 pF limits capacitive switching loss.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJD127G	V_CEO = −100 V, I_C = −2 A, h_FE = 30–240, TO-252 package	Higher voltage rating but wider h_FE spread; lower thermal resistance due to DPAK footprint	Preferred where higher breakdown margin or PCB-level thermal relief is required
BCP53-16	V_CEO = −45 V, I_C = −1.5 A, h_FE = 100–250, SOT-223 package	Lower power rating and smaller package; suitable only for ≤3 W loads	Selected for space-constrained designs where full 10 W dissipation is not needed

Compared with MJD127G and BCP53-16, the KSA1241YTU offers optimal balance of voltage margin, gain consistency (Y-class), and thermal capability in I-Pak-making it preferred for industrial audio and motor control where reliability under sustained 5–8 W dissipation matters.

Availability

KSA1241YTU is available at Aetrix Electronics and suitable for audio power amplifiers, DC motor drivers, linear regulators, and offline SMPS requiring stable component supply across production lifecycles.

Supply support for KSA1241YTU 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 designer and manufacturer of analog and discrete semiconductors, acquired by ON Semiconductor in 2016; known for robust power transistors and legacy automotive-grade components.

The KSA1241YTU belongs to Fairchild's high-reliability PNP power transistor family, engineered specifically for audio output stages and industrial switching where gain matching, saturation voltage stability, and thermal ruggedness are critical.

FAQ

What is the pin configuration of the KSA1241YTU?

The KSA1241YTU uses an I-Pak (TO-251AA) package with pin 1 = Base, pin 2 = Collector (tab-connected), and pin 3 = Emitter. This configuration is standardized across Fairchild's I-Pak PNP transistors and verified in the February 2000 Rev. A datasheet. Mounting orientation must ensure collector tab isolation from other conductive surfaces.

Is the KSA1241YTU RoHS compliant?

The KSA1241YTU was manufactured prior to RoHS enforcement and does not carry RoHS certification. Its lead-based terminations and packaging materials comply with pre-2006 industry standards. For new designs requiring RoHS compliance, consider ON Semiconductor's MJD127G or newer PNP alternatives with documented exemption status.

What is the hFE classification for KSA1241YTU?

The "YTU" suffix indicates Y-class h_FE, meaning guaranteed DC current gain of 120–240 at V_CE = −2 V and I_C = −1.5 A. This tighter binning supports matched-pair use with KSC3076 in push-pull amplifier outputs, reducing gain mismatch-induced distortion in the KSA1241YTU application.

Can KSA1241YTU replace KSA1220 in existing designs?

No-the KSA1220 has V_CEO = −30 V and I_C = −1.5 A, making it unsuitable as a drop-in replacement for KSA1241YTU in −50 V or −2 A applications. Substituting KSA1241YTU into a KSA1220 design may cause overvoltage stress on surrounding components due to higher breakdown ratings and different gain profile.

What thermal interface material is recommended for KSA1241YTU?

For optimal thermal performance, use a 0.1 mm thick thermally conductive silicone pad (e.g., Bergquist Sil-Pad 2000) between the KSA1241YTU collector tab and aluminum heatsink. Avoid thermal paste alone due to pump-out risk under thermal cycling; mechanical clamping pressure should be 25–40 psi to maintain interfacial contact integrity over time.

KSA1241YTU 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):: 2 A

Voltage - Collector Emitter Breakdown (Max):: 50 V

Vce Saturation (Max) @ Ib, Ic:: 500mV @ 50mA, 1A

Current - Collector Cutoff (Max):: 1µA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 120 @ 500mA, 2V

Power - Max:: 1 W

Frequency - Transition:: 100MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: IPAK

KSA1241YTU FAQ

1.How can I place an order for KSA1241YTU through Aetrix?

Please submit a Request for Quotation (RFQ) for KSA1241YTU 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 KSA1241YTU reliable?

The price and inventory of KSA1241YTU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for KSA1241YTU is usually 5 days.

3.What payment methods are accepted for KSA1241YTU?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for KSA1241YTU transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for KSA1241YTU?

KSA1241YTU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your KSA1241YTU 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 KSA1241YTU?

For technical support, including KSA1241YTU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your KSA1241YTU requirements.

6.How does Aetrix verify that KSA1241YTU is sourced from the original manufacturer or authorized distributors?

All KSA1241YTU 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 KSA1241YTU meets industry standards.

7.What is the process for return or replacement of KSA1241YTU?

All KSA1241YTU units undergo pre-shipment inspection (PSI). If there is an issue with KSA1241YTU, 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 KSA1241YTU part is unused and in its original packaging.

Return procedure for KSA1241YTU:

1.Submit a request within 90 days.

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

Tech Hub

2026-09-09 Counterfeit Electronic Components: How to Detect, Authenticate, and Test Suspect Parts

Counterfeit components can hide behind convincing markings and passing basic function tests. This engineering reference covers source traceability, external inspection, X-ray, XRF, electrical testing, …

2026-09-08 Obsolete Electronic Components: How to Source and Evaluate Replacements

A practical engineering and sourcing framework covering lifecycle verification, lifetime-buy calculations, replacement qualification, supplier checks and counterfeit-risk controls.

2026-09-07 TTL vs CMOS Logic Levels: 74HC and 74HCT Compatibility Explained

TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.

2026-09-04 Logic Level Shifter: How to Connect 3.3V and 5V Logic Safely

A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.

2026-09-03 74HC595 vs TPIC6B595: Output Drive, Pinout, Current, and Load Selection

The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…

2026-09-02 74HC595 Pinout, Timing, Output Current, and Applications

The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…

2026-09-01 Latch vs Flip-Flop: Timing, Differences and Design Choices

A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…

2026-08-30 D Latch Circuit: Truth Table, Timing, ICs and Applications

A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …

2026-08-28 SR Latch Explained: NOR and NAND Circuits, Truth Tables, and Applications

An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…

2026-08-27 Latch Circuit: SR and D Latches, Truth Tables, Timing, and Applications

Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…