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

onsemi KSA1381ESTSTU

Name: KSA1381ESTSTU
Brand: onsemi
SKU: KSA1381ESTSTU
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: KSA1381ESTSTU

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-225AA, TO-126-3

Datasheet:: KSA1381ESTSTU.pdf

Description:: TRANS PNP 300V 0.1A TO-126-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

KSA1381ESTSTU from onsemi is a PNP epitaxial silicon transistor rated for −300 V collector-emitter and collector-base breakdown, 150 MHz current gain bandwidth, 100–200 DC current gain at −10 mA, and −100 mA continuous collector current - used in CRT video output stages and high-voltage audio amplifiers.

For engineers reviewing the KSA1381ESTSTU datasheet, pinout, applications, or equivalent options, key selection criteria include high-voltage PNP capability, low Cre (2.3 pF), gain linearity for low THD, TO-126-3LD thermal performance (R_JC = 17.8°C/W), and complementarity to KSC3503.

Technical Context

This device operates as a high-voltage, medium-frequency PNP bipolar junction transistor with fully characterized thermal resistance (17.8°C/W junction-to-case) and validated Spice models. Its −300 V BVCBO/BVCEO ratings enable use in flyback and deflection circuits where voltage transients exceed 250 V.

The KSA1381ESTSTU delivers linear h_FE response across −1 to −20 mA collector currents and maintains low reverse transfer capacitance (Cre = 2.3 pF at −30 V), supporting stable high-frequency amplification without oscillation in grounded-emitter configurations.

Key Specifications

Parameter	Value and Actual Design Meaning
BV_CEO	−300 V - supports operation in CRT horizontal deflection and high-side switching up to 300 V reverse bias without breakdown
f_T	150 MHz - enables stable small-signal amplification in video driver and RF preamp stages up to VHF band
h_FE	100–200 at −10 mA - provides predictable current amplification for Class-A/B audio output and precision current source design
C_re	2.3 pF at V_CB = −30 V - minimizes Miller effect and improves stability in high-gain common-emitter video amplifier topologies
R_JC	17.8°C/W - allows 7 W dissipation at T_C = 25°C, enabling heatsink-free operation in low-duty-cycle pulse applications
V_CE(sat)	≤ −0.6 V at I_C = −20 mA, I_B = −2 mA - ensures low conduction loss in active-load and constant-current sink configurations

Pinout & Package

Package: TO-126-3LD (Case 340AS), Pb-free, through-hole, 3-pin plastic power package with tab-connected collector for direct heatsinking.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Emitter terminal	Reference node for base drive; polarity defines PNP operation - must be held at highest potential in circuit
2 (Collector)	Collector terminal	Connected to internal metal tab; electrically and thermally coupled to heatsink - carries full load current and dissipates heat
3 (Base)	Base control terminal	Current-controlled input; requires negative bias relative to emitter to turn on; low input impedance demands robust driver stage

Key Features

Feature	Design Value
High-voltage PNP structure	−300 V BV_CEO/BV_CBO enables direct replacement of legacy high-voltage PNP transistors in CRT and industrial power supplies
Low Cre capacitance	2.3 pF reverse transfer capacitance reduces feedback coupling in wideband amplifiers, improving phase margin and reducing peaking
Gain linearity	h_FE variation <±15% over I_C = −1 to −20 mA ensures low harmonic distortion in analog audio and video signal paths
Thermal model availability	Full thermal and electrical Spice models support accurate transient simulation of power dissipation and junction temperature rise

Applications

CRT Horizontal Deflection	High-Voltage Audio Amplifier
Use Scenario: Driving flyback transformer primary in monochrome or color CRT monitors requiring precise timing and high-voltage swing. IC Role / Device Role / Timing Role: High-voltage PNP switch in self-oscillating or synchronized horizontal output stage. Use Value: −300 V rating withstands flyback spikes; 150 MHz f_T ensures clean edge fidelity during rapid switching transitions.	Use Scenario: Output stage in discrete Class-AB audio amplifiers targeting low-THD performance above 20 kHz. IC Role / Device Role / Timing Role: Complementary PNP output transistor paired with NPN KSC3503 in push-pull configuration. Use Value: Linear h_FE and low Cre minimize intermodulation distortion; TO-126 package enables direct heatsink mounting for thermal stability.
Video Signal Driver	Constant Current Source
Use Scenario: Active load or cathode follower in RGB video output buffers for analog display interfaces. IC Role / Device Role / Timing Role: High-impedance, high-linearity current source for biasing video DAC output stages. Use Value: Stable h_FE across operating range ensures consistent current mirroring; low Cob (3.1 pF) preserves signal integrity up to 10 MHz.	Use Scenario: Precision current sink in LED biasing, sensor excitation, or reference current generation circuits. IC Role / Device Role / Timing Role: Regulated current source using emitter-degeneration resistor and fixed base bias. Use Value: −100 mA I_C rating and ≤−0.6 V V_CE(sat) allow sub-100 mW dissipation at 1 mA–10 mA sink currents with minimal voltage headroom.

CRT Horizontal Deflection

High-Voltage Audio Amplifier

Use Scenario: Driving flyback transformer primary in monochrome or color CRT monitors requiring precise timing and high-voltage swing.

IC Role / Device Role / Timing Role: High-voltage PNP switch in self-oscillating or synchronized horizontal output stage.

Use Value: −300 V rating withstands flyback spikes; 150 MHz f_T ensures clean edge fidelity during rapid switching transitions.

Use Scenario: Output stage in discrete Class-AB audio amplifiers targeting low-THD performance above 20 kHz.

IC Role / Device Role / Timing Role: Complementary PNP output transistor paired with NPN KSC3503 in push-pull configuration.

Use Value: Linear h_FE and low Cre minimize intermodulation distortion; TO-126 package enables direct heatsink mounting for thermal stability.

Video Signal Driver

Constant Current Source

Use Scenario: Active load or cathode follower in RGB video output buffers for analog display interfaces.

IC Role / Device Role / Timing Role: High-impedance, high-linearity current source for biasing video DAC output stages.

Use Value: Stable h_FE across operating range ensures consistent current mirroring; low Cob (3.1 pF) preserves signal integrity up to 10 MHz.

Use Scenario: Precision current sink in LED biasing, sensor excitation, or reference current generation circuits.

IC Role / Device Role / Timing Role: Regulated current source using emitter-degeneration resistor and fixed base bias.

Use Value: −100 mA I_C rating and ≤−0.6 V V_CE(sat) allow sub-100 mW dissipation at 1 mA–10 mA sink currents with minimal voltage headroom.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
KSA992FBU	Same TO-126 package; BV_CEO = −200 V (100 V lower); h_FE = 60–120; f_T = 80 MHz	Limited to ≤200 V applications; reduced bandwidth and gain linearity vs. KSA1381ESTSTU	Select when cost sensitivity outweighs voltage or frequency requirements
MJD44H11T4G	TO-220 package; BV_CEO = −80 V; I_C = −8 A; higher power but much lower voltage rating	Not suitable for CRT or high-voltage analog; intended for motor control and industrial switching	Choose only for high-current, low-voltage switching - not a functional substitute for KSA1381ESTSTU

Compared with KSA992FBU and MJD44H11T4G, the KSA1381ESTSTU uniquely combines −300 V rating, 150 MHz bandwidth, and TO-126 thermal efficiency - making it irreplaceable in CRT deflection and high-fidelity high-voltage analog stages where both voltage headroom and signal fidelity are critical.

Availability

KSA1381ESTSTU is available at Aetrix Electronics and suitable for CRT display systems, high-voltage audio amplifiers, and video signal drivers requiring stable component supply and long-lifecycle support.

Supply support for KSA1381ESTSTU 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 supplier specializing in energy-efficient power, analog, sensors, and connectivity solutions for automotive, industrial, and cloud power markets.

The KSA1381ESTSTU belongs to onsemi's high-voltage bipolar transistor product line, engineered specifically for CRT deflection, analog video, and high-fidelity audio applications demanding ruggedness, linearity, and thermal reliability.

FAQ

What is the maximum collector-emitter voltage rating for the KSA1381ESTSTU?

The KSA1381ESTSTU has a guaranteed BV_CEO of −300 V at I_C = −1 mA and I_B = 0. This rating is validated per onsemi's absolute maximum ratings table and applies under DC and pulsed conditions within safe operating area limits. Exceeding −300 V risks irreversible breakdown. The KSA1381ESTSTU must be operated with appropriate snubbing and clamping in flyback circuits to avoid transient overshoot beyond this limit.

Is the KSA1381ESTSTU pin-compatible with the KSC3503 NPN transistor?

No - the KSA1381ESTSTU (PNP) and KSC3503 (NPN) are complementary devices, not pin-compatible. Both use TO-126 packages with identical pinout order (Emitter-Collector-Base), but their polarity and biasing requirements differ fundamentally. The KSA1381ESTSTU requires negative base drive relative to emitter, while the KSC3503 needs positive base drive. Circuit redesign is required when substituting one for the other.

Does the KSA1381ESTSTU have SPICE models available for simulation?

Yes - onsemi provides full thermal and electrical SPICE models for the KSA1381ESTSTU, including temperature-dependent parameters and parasitic capacitances. These models are validated against measured f_T, C_ob, Cre, and saturation characteristics. Engineers can download them directly from the official onsemi website under the KSA1381 product page or via the "Design Resources" portal.

What is the thermal resistance junction-to-case for the KSA1381ESTSTU?

The KSA1381ESTSTU has a specified R_JC of 17.8°C/W when mounted on minimum pad size per onsemi's thermal characterization note. This value assumes direct thermal contact between the collector tab and an external heatsink. Derating is required above 25°C case temperature - at T_C = 125°C, maximum power dissipation drops to 1.2 W, as confirmed in the Absolute Maximum Ratings table.

Can the KSA1381ESTSTU be used in surface-mount designs?

No - the KSA1381ESTSTU is exclusively offered in the through-hole TO-126-3LD package (Case 340AS). It lacks a surface-mount variant. Attempting to mount it on SMT pads without mechanical anchoring and proper lead forming will compromise thermal performance and long-term reliability. For SMT alternatives, engineers should evaluate onsemi's MMBT series or other qualified SOT-223/SOT-89 PNP transistors - but none match its −300 V rating.

KSA1381ESTSTU Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-225AA, TO-126-3

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: PNP

Current - Collector (Ic) (Max):: 100 mA

Voltage - Collector Emitter Breakdown (Max):: 300 V

Vce Saturation (Max) @ Ib, Ic:: 600mV @ 2mA, 20mA

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

DC Current Gain (hFE) (Min) @ Ic, Vce:: 100 @ 10mA, 10V

Power - Max:: 7 W

Frequency - Transition:: 150MHz

Operating Temperature:: -55°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-126-3

KSA1381ESTSTU FAQ

1.How can I place an order for KSA1381ESTSTU through Aetrix?

Please submit a Request for Quotation (RFQ) for KSA1381ESTSTU 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 KSA1381ESTSTU reliable?

The price and inventory of KSA1381ESTSTU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for KSA1381ESTSTU is usually 5 days.

3.What payment methods are accepted for KSA1381ESTSTU?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for KSA1381ESTSTU transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for KSA1381ESTSTU?

KSA1381ESTSTU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your KSA1381ESTSTU 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 KSA1381ESTSTU?

For technical support, including KSA1381ESTSTU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your KSA1381ESTSTU requirements.

6.How does Aetrix verify that KSA1381ESTSTU is sourced from the original manufacturer or authorized distributors?

All KSA1381ESTSTU 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 KSA1381ESTSTU meets industry standards.

7.What is the process for return or replacement of KSA1381ESTSTU?

All KSA1381ESTSTU units undergo pre-shipment inspection (PSI). If there is an issue with KSA1381ESTSTU, 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 KSA1381ESTSTU part is unused and in its original packaging.

Return procedure for KSA1381ESTSTU:

1.Submit a request within 90 days.

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

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