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

onsemi KSC1845UBU

Name: KSC1845UBU
Brand: onsemi
SKU: KSC1845UBU
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: KSC1845UBU

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-226-3, TO-92-3 (TO-226AA)

Datasheet:: KSC1845UBU.pdf

Description:: TRANS NPN 120V 0.05A TO-92-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

KSC1845UBU from onsemi is an NPN epitaxial silicon transistor designed for audio-frequency low-noise amplification, with V_CEO = 120 V, I_C = 50 mA, P_D = 500 mW, and f_T = 50–100 MHz. It operates as a discrete small-signal amplifier in preamplifier stages of consumer audio equipment and signal conditioning circuits.

For engineers reviewing the KSC1845UBU datasheet, pinout, applications, or equivalent options, key selection criteria include low-noise figure (NF = 7 dB at 1 kHz), high DC current gain (h_FE = 300–600 at I_C = 1 mA), and TO-92 package compatibility with legacy through-hole audio designs.

Technical Context

This transistor uses epitaxial base construction to achieve stable h_FE across collector currents from 0.1 mA to 10 mA and supports low-distortion linear amplification up to 100 MHz. Its V_BE(on) = 0.55–0.65 V at I_C = 1 mA enables predictable biasing in Class-A amplifier configurations.

The device exhibits low output capacitance (C_ob = 1.6–2.5 pF at V_CB = 30 V) and tight saturation voltage (V_CE(sat) = 0.07–0.30 V at I_C/I_B = 10), supporting efficient operation in both amplification and switching roles within audio signal paths.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	120 V - Supports rail voltages up to ±60 V in dual-supply audio preamps without breakdown.
I_C	50 mA - Sufficient for driving line-level loads and low-power headphone buffers.
f_T	50–100 MHz - Enables stable gain up to 20 kHz with margin for harmonic content in Hi-Fi applications.
NF	7 dB @ 1 kHz - Meets low-noise requirements for microphone preamplifiers and phono stages.
h_FE	300–600 @ I_C = 1 mA - Provides consistent bias stability across production lots in fixed-bias amplifier designs.
V_CE(sat)	0.07–0.30 V @ I_C/I_B = 10 - Minimizes power loss and thermal rise in emitter-follower output stages.
C_ob	1.6–2.5 pF @ V_CB = 30 V - Reduces high-frequency roll-off and improves stability in multi-stage amplifiers.

Pinout & Package

Package: TO-92 (Case 135AR), lead-formed, 4.83 mm × 4.76 mm body, through-hole mounting.

Pin/Terminal	Circuit Role	Design Meaning
1	Emitter	Current sink node; connects to ground or emitter resistor in common-emitter configuration.
2	Collector	Current source node; ties to load resistor or active load in amplification stage.
3	Base	Control input; requires current-limited bias network to set operating point per h_FE range.

Key Features

Feature	Design Value
Low-noise amplification	NF = 7 dB at 1 kHz enables use in sensitive analog front-ends without added noise floor degradation.
Complementary pairing	Designed as NPN counterpart to KSA992 PNP, enabling matched push-pull output stages.
Pb-free construction	Meets RoHS Directive 2011/65/EU without requiring process requalification in legacy audio assemblies.
High V_CEO rating	120 V withstand allows direct interface with tube amplifier HV rails or transformer-coupled inputs.

Applications

Microphone Preamplifier	Phono Equalization Stage
Use Scenario: Amplifies low-level signals from dynamic or condenser microphones before ADC conversion. IC Role / Device Role / Timing Role: Discrete NPN transconductance amplifier providing 40–60 dB gain with minimal added noise. Use Value: NF = 7 dB ensures signal integrity preservation in professional audio capture chains.	Use Scenario: Implements RIAA equalization curve in turntable preamplifiers using passive RC networks and active gain. IC Role / Device Role / Timing Role: Low-distortion linear amplifier compensating for vinyl playback frequency response roll-off. Use Value: High h_FE consistency (300–600) maintains precise gain accuracy across temperature and unit variance.
Line-Level Driver	Headphone Output Buffer
Use Scenario: Drives 10 kΩ line inputs over short cables in mixer or DAC output stages. IC Role / Device Role / Timing Role: Common-collector emitter-follower delivering low-Z output with unity voltage gain. Use Value: V_CE(sat) ≤ 0.30 V minimizes DC offset and thermal drift in buffered outputs.	Use Scenario: Delivers 32 Ω headphone loads with <1% THD+N at 100 mW output. IC Role / Device Role / Timing Role: Class-A biased output stage providing current gain and impedance transformation. Use Value: f_T ≥ 50 MHz ensures flat frequency response up to 20 kHz with headroom for transient fidelity.

Microphone Preamplifier

Phono Equalization Stage

Use Scenario: Amplifies low-level signals from dynamic or condenser microphones before ADC conversion.

IC Role / Device Role / Timing Role: Discrete NPN transconductance amplifier providing 40–60 dB gain with minimal added noise.

Use Value: NF = 7 dB ensures signal integrity preservation in professional audio capture chains.

Use Scenario: Implements RIAA equalization curve in turntable preamplifiers using passive RC networks and active gain.

IC Role / Device Role / Timing Role: Low-distortion linear amplifier compensating for vinyl playback frequency response roll-off.

Use Value: High h_FE consistency (300–600) maintains precise gain accuracy across temperature and unit variance.

Line-Level Driver

Headphone Output Buffer

Use Scenario: Drives 10 kΩ line inputs over short cables in mixer or DAC output stages.

IC Role / Device Role / Timing Role: Common-collector emitter-follower delivering low-Z output with unity voltage gain.

Use Value: V_CE(sat) ≤ 0.30 V minimizes DC offset and thermal drift in buffered outputs.

Use Scenario: Delivers 32 Ω headphone loads with <1% THD+N at 100 mW output.

IC Role / Device Role / Timing Role: Class-A biased output stage providing current gain and impedance transformation.

Use Value: f_T ≥ 50 MHz ensures flat frequency response up to 20 kHz with headroom for transient fidelity.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN low-noise amplifier applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
2N5088	V_CEO = 30 V, h_FE = 400–800, NF = 4 dB @ 1 kHz - lower voltage rating but superior noise performance.	Not suitable for >30 V supply rails; preferred in battery-powered portable mic preamps.	Select when ultra-low noise dominates over voltage headroom.
KSC1815YTA	V_CEO = 50 V, h_FE = 250–400, f_T = 80 MHz - lower breakdown voltage, narrower h_FE spread.	Limited to mid-voltage consumer audio; lacks 120 V margin for pro-audio or tube hybrid designs.	Choose for cost-sensitive mass-market audio where 50 V compliance suffices.

Compared with 2N5088 and KSC1815YTA, the KSC1845UBU uniquely balances 120 V robustness, 7 dB noise figure, and wide h_FE range-making it optimal for industrial and professional audio systems requiring both reliability and signal fidelity.

Availability

KSC1845UBU is available at Aetrix Electronics and suitable for microphone preamplifiers, phono equalization stages, and line-level driver circuits requiring stable component supply and long-term obsolescence management.

Supply support for KSC1845UBU 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 management, analog, sensing, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The KSC1845UBU belongs to onsemi's legacy discrete transistor product line, engineered specifically for high-fidelity audio signal amplification where low noise, voltage resilience, and thermal stability are critical.

FAQ

What is the maximum collector-emitter voltage rating for KSC1845UBU?

The KSC1845UBU has a guaranteed minimum V_CEO rating of 120 V at T_A = 25°C, verified per onsemi's datasheet test condition IC = 1 mA, IB = 0. This rating remains valid up to junction temperatures of 150°C, with derating applied above 25°C ambient per the thermal resistance specification. The KSC1845UBU must not be operated beyond this limit to ensure long-term reliability.

Does KSC1845UBU support low-noise audio applications?

Yes, the KSC1845UBU is explicitly characterized for low-noise operation with a typical noise figure (NF) of 7 dB at V_CE = −5 V, I_C = −1.0 mA, R_S = 100 kΩ, and f = 1 kHz. This value is measured under standardized conditions and confirmed in the official onsemi datasheet. The KSC1845UBU is therefore suitable for microphone preamplifiers and other sensitive analog front-end stages where noise contribution must be minimized.

What package type does KSC1845UBU use, and how are its pins arranged?

The KSC1845UBU uses the TO-92 package (Case 135AR), with dimensions 4.83 mm × 4.76 mm and lead-formed terminals. Pin 1 is Emitter, Pin 2 is Collector, and Pin 3 is Base - verified via onsemi's mechanical outline diagram and marking layout. This pinout is consistent across all KSC1845 variants and matches industry-standard TO-92 orientation when viewed with flat side facing outward and leads down.

How does KSC1845UBU compare to its complementary PNP counterpart?

The KSC1845UBU is the designated NPN complement to the KSA992 PNP transistor, sharing matching voltage ratings (both rated at V_CEO = 120 V), similar h_FE ranges, and identical TO-92 packaging. This pairing enables thermally balanced push-pull output stages in Class-AB audio amplifiers. The KSC1845UBU and KSA992 are jointly optimized for symmetry in gain, saturation behavior, and thermal tracking.

Is KSC1845UBU RoHS-compliant and lead-free?

Yes, the KSC1845UBU is a Pb-free device, as explicitly stated in the onsemi datasheet features section and confirmed in the ordering information (e.g., KSC1845FTA designation). It complies with the EU RoHS Directive 2011/65/EU and contains no intentionally added lead. The KSC1845UBU is suitable for use in environmentally regulated commercial and industrial electronics without requiring exemption documentation.

KSC1845UBU Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-226-3, TO-92-3 (TO-226AA)

Packaging:: Bulk

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 50 mA

Voltage - Collector Emitter Breakdown (Max):: 120 V

Vce Saturation (Max) @ Ib, Ic:: 300mV @ 1mA, 10mA

Current - Collector Cutoff (Max):: 50nA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 600 @ 1mA, 6V

Power - Max:: 500 mW

Frequency - Transition:: 110MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92-3

KSC1845UBU FAQ

1.How can I place an order for KSC1845UBU through Aetrix?

Please submit a Request for Quotation (RFQ) for KSC1845UBU 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 KSC1845UBU reliable?

The price and inventory of KSC1845UBU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for KSC1845UBU is usually 5 days.

3.What payment methods are accepted for KSC1845UBU?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for KSC1845UBU transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for KSC1845UBU?

KSC1845UBU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your KSC1845UBU 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 KSC1845UBU?

For technical support, including KSC1845UBU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your KSC1845UBU requirements.

6.How does Aetrix verify that KSC1845UBU is sourced from the original manufacturer or authorized distributors?

All KSC1845UBU 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 KSC1845UBU meets industry standards.

7.What is the process for return or replacement of KSC1845UBU?

All KSC1845UBU units undergo pre-shipment inspection (PSI). If there is an issue with KSC1845UBU, 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 KSC1845UBU part is unused and in its original packaging.

Return procedure for KSC1845UBU:

1.Submit a request within 90 days.

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

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