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 KSA1281YBU

Name: KSA1281YBU
Brand: onsemi
SKU: KSA1281YBU
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: KSA1281YBU

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-226-3, TO-92-3 Long Body

Datasheet:: KSA1281YBU.pdf

Description:: TRANS PNP 50V 2A TO-92-3

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:4,878

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

Product details

Overview

KSA1281YBU from onsemi is a PNP epitaxial silicon transistor designed for audio power amplifier stages, delivering up to 3 W output with −50 V collector-emitter breakdown voltage, −2 A continuous collector current, and 100 MHz transition frequency in TO-92 3L package.

For engineers reviewing the KSA1281YBU datasheet, pinout, applications, or equivalent options, key selection criteria include safe operating area at high current, low V_CE(sat) of −0.5 V at −1 A, thermal resistance of 125 °C/W, and compatibility with Class AB audio output stages requiring robust PNP complement to NPN drivers.

Technical Context

This device operates as a medium-power PNP bipolar junction transistor optimized for linear amplification. Its DC current gain ranges from 120–240 at −500 mA and drops to ≥40 at −1.5 A, supporting both small-signal biasing and high-current swing in push-pull configurations.

Thermal design is constrained by 1000 mW maximum power dissipation at T_C = 25 °C and 8.0 mW/°C derating above ambient, requiring careful heatsinking in sustained 3 W output applications. Output capacitance of 40 pF at −10 V V_CB supports stable operation up to 100 MHz f_T.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	−50 V: Maximum allowable collector-emitter voltage before breakdown in common-emitter configuration.
I_C	−2 A: Continuous collector current rating defining maximum linear output capability.
f_T	100 MHz: Transition frequency enabling use in audio bandwidth amplifiers with margin into RF edge.
V_CE(sat)	−0.5 V at I_C = −1 A, I_B = −0.05 A: Low saturation voltage minimizes power loss in switching or saturated output stages.
h_FE	120–240 at I_C = −500 mA: Sufficient DC gain for direct-coupled driver stages without excessive base drive.
R_JA	125 °C/W: Junction-to-ambient thermal resistance under standard FR-4 PCB conditions (76 mm × 114 mm).

Pinout & Package

Package: TO-92 3L (Case 135AM), lead-formed, plastic molded, through-hole mounting. Dimensions: 8.0 mm × 4.9 mm.

Pin/Terminal	Circuit Role	Design Meaning
1	Emitter	Current sink terminal; connects to ground or negative rail in common-emitter amplifier.
2	Collector	Current source terminal; connects to load and positive supply via pull-up or transformer coupling.
3	Base	Control input; requires current-limited drive to achieve specified h_FE and saturation behavior.

Key Features

Feature	Design Value
Audio power amplifier grade	Optimized for low-distortion linear operation in Class AB output stages up to 3 W.
High breakdown voltage	−50 V V_CEO enables use with ±24 V rails and transient-tolerant designs.
Low saturation voltage	V_CE(sat) = −0.5 V reduces conduction loss and improves efficiency in saturated switching or clipping regions.
Stable gain across current range	h_FE ≥40 at −1.5 A ensures predictable base drive requirements even near maximum current.

Applications

Audio Power Amplifier	DC Motor Driver Stage
Use Scenario: Final output stage in portable stereo amplifier driving 4–8 Ω speakers. IC Role / Device Role / Timing Role: PNP complement in push-pull emitter-follower configuration delivering bidirectional current to speaker load. Use Value: −0.5 V V_CE(sat) and 100 MHz f_T support clean mid-band response and low crossover distortion.	Use Scenario: H-bridge low-side PNP switch controlling direction and braking in 12 V brushed DC motor. IC Role / Device Role / Timing Role: High-current sinking switch turning motor winding to ground during active braking. Use Value: −2 A I_C rating and −50 V V_CEO withstand back-EMF spikes during commutation.
Power Supply Pass Transistor	Linear Voltage Regulator Output Stage
Use Scenario: Series pass element in adjustable negative linear regulator (e.g., −5 V to −15 V output). IC Role / Device Role / Timing Role: Controlled current sink regulating output voltage via feedback to base. Use Value: 120–240 h_FE allows stable closed-loop control with minimal base drive error.	Use Scenario: Output transistor in discrete negative LDO for analog sensor biasing. IC Role / Device Role / Timing Role: Precision current-controlled emitter follower maintaining low-noise, ripple-free output. Use Value: 40 pF Cob and 100 MHz f_T ensure fast transient response to load steps without oscillation.

Audio Power Amplifier

DC Motor Driver Stage

Use Scenario: Final output stage in portable stereo amplifier driving 4–8 Ω speakers.

IC Role / Device Role / Timing Role: PNP complement in push-pull emitter-follower configuration delivering bidirectional current to speaker load.

Use Value: −0.5 V V_CE(sat) and 100 MHz f_T support clean mid-band response and low crossover distortion.

Use Scenario: H-bridge low-side PNP switch controlling direction and braking in 12 V brushed DC motor.

IC Role / Device Role / Timing Role: High-current sinking switch turning motor winding to ground during active braking.

Use Value: −2 A I_C rating and −50 V V_CEO withstand back-EMF spikes during commutation.

Power Supply Pass Transistor

Linear Voltage Regulator Output Stage

Use Scenario: Series pass element in adjustable negative linear regulator (e.g., −5 V to −15 V output).

IC Role / Device Role / Timing Role: Controlled current sink regulating output voltage via feedback to base.

Use Value: 120–240 h_FE allows stable closed-loop control with minimal base drive error.

Use Scenario: Output transistor in discrete negative LDO for analog sensor biasing.

IC Role / Device Role / Timing Role: Precision current-controlled emitter follower maintaining low-noise, ripple-free output.

Use Value: 40 pF Cob and 100 MHz f_T ensure fast transient response to load steps without oscillation.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJD127G	TO-220 package, higher P_D (15 W), lower f_T (3 MHz), same V_CEO/I_C ratings.	Suitable for higher-power audio or industrial switching where heatsink mounting is feasible.	Select when >3 W output or forced-air cooling is required; not drop-in due to package and thermal profile.
KSA992FBU	Same TO-92 3L package, lower V_CEO (−30 V), higher h_FE (200–400), reduced I_C (−1.5 A).	Better for low-voltage, high-gain pre-driver stages rather than full 3 W output.	Choose for compact low-voltage designs where gain stability at low current matters more than peak power.

Compared with MJD127G and KSA992FBU, the KSA1281YBU uniquely balances TO-92 mountability, 3 W audio-grade output, and 100 MHz f_T, making it optimal for space-constrained linear amplifiers needing both bandwidth and thermal manageability on standard PCBs.

Availability

KSA1281YBU is available at Aetrix Electronics and suitable for audio power amplifiers, DC motor control circuits, and linear voltage regulators requiring stable component supply with consistent TO-92 3L mechanical and electrical performance.

Supply support for KSA1281YBU 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 is a global semiconductor supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The KSA1281YBU belongs to onsemi's general-purpose bipolar transistor product line, engineered specifically for cost-sensitive, medium-power linear and switching applications demanding reliability in consumer and industrial audio systems.

FAQ

What is the maximum continuous collector current rating for KSA1281YBU?

The KSA1281YBU has a maximum continuous collector current (I_C) rating of −2 A at T_A = 25 °C. This rating assumes proper PCB thermal management per the datasheet's FR-4 reference layout. Derating applies above ambient temperature, with 8.0 mW/°C reduction beyond 25 °C. The KSA1281YBU must not be operated beyond this limit without verified heatsinking or airflow.

Does KSA1281YBU support audio amplifier applications up to 3 W output?

Yes, the KSA1281YBU is explicitly characterized for audio power amplifier use with up to 3 W output capability. Its combination of −50 V V_CEO, −2 A I_C, −0.5 V V_CE(sat), and 100 MHz f_T meets the voltage, current, efficiency, and bandwidth requirements of Class AB output stages driving 4–8 Ω loads. The KSA1281YBU datasheet confirms this application in its Features section and Safe Operating Area curves.

What is the pin configuration of KSA1281YBU in TO-92 3L package?

The KSA1281YBU uses standard TO-92 3L pinout: Pin 1 is Emitter, Pin 2 is Collector, and Pin 3 is Base - viewed from the flat side with leads pointing downward. This matches Case 135AM mechanical outline and is confirmed in the "PIN CONNECTIONS" diagram on page 1 of the official onsemi datasheet. The KSA1281YBU must be mounted with correct orientation to avoid functional failure.

Is KSA1281YBU RoHS compliant and halogen-free?

Yes, the KSA1281YBU is RoHS compliant and halogen-free per onsemi's product compliance documentation. It meets EU Directive 2011/65/EU and IEC 61249-2-21:2012 standards. The material declaration and environmental compliance status for KSA1281YBU are published on onsemi's website under "Product Compliance" and verified for all manufacturing lots shipped since 2021. KSA1281YBU carries no exemptions requiring special handling.

What is the typical DC current gain (h_FE) of KSA1281YBU at different operating points?

The KSA1281YBU exhibits h_FE = 120–240 at V_CE = −2 V and I_C = −500 mA, and h_FE ≥ 40 at V_CE = −2 V and I_C = −1.5 A. These values are measured under pulsed conditions per Note 2 in the datasheet. Gain decreases predictably with increasing current, and the KSA1281YBU maintains usable gain across its rated output range, supporting stable bias networks in audio and power applications.

KSA1281YBU Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-226-3, TO-92-3 Long Body

Packaging:: Bulk

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):: 100nA (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:: TO-92-3

KSA1281YBU FAQ

1.How can I place an order for KSA1281YBU through Aetrix?

Please submit a Request for Quotation (RFQ) for KSA1281YBU 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 KSA1281YBU reliable?

The price and inventory of KSA1281YBU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for KSA1281YBU is usually 5 days.

3.What payment methods are accepted for KSA1281YBU?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for KSA1281YBU transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for KSA1281YBU?

KSA1281YBU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your KSA1281YBU 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 KSA1281YBU?

For technical support, including KSA1281YBU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your KSA1281YBU requirements.

6.How does Aetrix verify that KSA1281YBU is sourced from the original manufacturer or authorized distributors?

All KSA1281YBU 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 KSA1281YBU meets industry standards.

7.What is the process for return or replacement of KSA1281YBU?

All KSA1281YBU units undergo pre-shipment inspection (PSI). If there is an issue with KSA1281YBU, 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 KSA1281YBU part is unused and in its original packaging.

Return procedure for KSA1281YBU:

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…