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

onsemi KSC2784PBU

Name: KSC2784PBU
Brand: onsemi
SKU: KSC2784PBU
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: KSC2784PBU

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: KSC2784PBU.pdf

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

Quantity:: RFQ Add To RFQ list

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Product details

Overview

KSC2784PBU from Fairchild Semiconductor is an NPN epitaxial silicon transistor optimized for audio-frequency low-noise amplification, with V_CEO = 120 V, I_C = 50 mA, P_C = 300 mW, and hFE2 classification of 600–1200 at I_C = 1 mA. It serves as a low-noise active device in preamplifier stages of consumer audio equipment.

For engineers reviewing the KSC2784PBU datasheet, pinout, applications, or equivalent options, key selection criteria include its 25–40 mV noise level, f_T up to 110 MHz, V_CE(sat) ≤ 0.3 V at I_C = 10 mA/I_B = 1 mA, and TO-92S package compatibility with through-hole audio signal chains.

Technical Context

This transistor operates in linear active mode for analog signal amplification, featuring a high DC current gain (hFE2 = 600–1200) and low base-emitter on-voltage (V_BE(on) = 0.55–0.65 V at I_C = 1 mA). Its 1.6–2.5 pF output capacitance and 50–110 MHz f_T support stable gain in audio-band circuits up to ~20 kHz with margin.

The device is specified for T_J = 150°C maximum junction temperature and T_STG = –55 to 150°C storage range, with absolute ratings including V_CBO = V_CEO = 120 V and V_EBO = 5 V - enabling use in bias-stable, medium-voltage audio front-ends where leakage (I_CBO, I_EBO ≤ 50 nA) must be minimized.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	120 V - supports operation in single-supply audio stages up to ±60 V rails without breakdown
I_C	50 mA - sufficient collector current headroom for line-level and headphone driver preamp loads
P_C	300 mW - enables continuous operation in thermally unassisted TO-92S packages at ambient ≤ 70°C
hFE2	600–1200 - ensures consistent small-signal gain stability across production lots at I_C = 1 mA
f_T	50–110 MHz - provides >5× bandwidth margin over 20 kHz audio band, reducing phase distortion
NL	25–40 mV - quantifies inherent wideband noise floor critical for microphone and phono preamp SNR
V_CE(sat)	0.07–0.3 V - minimizes voltage drop and power loss in emitter-follower or Class-A bias configurations

Pinout & Package

Package: TO-92S (3-lead, straight-lead, small-outline plastic). Dimensions conform to JEDEC TO-92S standard with lead spacing 1.27 mm and body height 4.00 mm ±0.20 mm.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current sink terminal	Connected to ground or low-impedance return path in common-emitter amplifier topologies
2 (Collector)	Current source terminal	Drives load impedance (e.g., transformer primary or next-stage base) with minimal saturation loss
3 (Base)	Control input terminal	Receives bias current (≤10 mA max) to set operating point; sensitive to ESD due to V_EBO = 5 V limit

Key Features

Feature	Design Value
Low noise level (25–40 mV)	Enables high-fidelity signal amplification in microphone preamps without degrading SNR below 85 dB
High hFE2 classification (600–1200)	Reduces required base drive current and improves input impedance matching in discrete gain stages
TO-92S package	Supports manual assembly and rework in prototyping while maintaining thermal resistance < 300°C/W
Complementary pairing with KSA1174	Allows balanced push-pull or differential amplifier designs using matched NPN/PNP characteristics
V_CE(sat) ≤ 0.3 V @ 10 mA/1 mA	Minimizes quiescent power dissipation in Class-A audio stages, extending thermal margin

Applications

Microphone Preamp	Phono Stage Amplifier
Use Scenario: Amplifying low-level signals from dynamic or condenser microphones before ADC or tone control. IC Role / Device Role / Timing Role: Discrete NPN transconductance amplifier in first gain stage with emitter degeneration. Use Value: 25–40 mV noise level preserves signal integrity; hFE2 ≥ 600 ensures stable gain without feedback instability.	Use Scenario: RIAA-equalized amplification of vinyl playback cartridge outputs (typically 5 mV RMS). IC Role / Device Role / Timing Role: High-input-impedance common-emitter amplifier with precise DC biasing. Use Value: V_CEO = 120 V accommodates RIAA network voltage swings; low Cob (1.6–2.5 pF) avoids high-frequency roll-off.
Headphone Driver Buffer	Instrument Input Stage
Use Scenario: Low-distortion unity-gain buffer driving 16–32 Ω headphones from line-level sources. IC Role / Device Role / Timing Role: Emitter-follower output stage with local negative feedback. Use Value: V_CE(sat) ≤ 0.3 V ensures ≥ 2 V peak output swing into 32 Ω; P_C = 300 mW prevents thermal shutdown during sustained bass transients.	Use Scenario: High-Z input conditioning for electric guitar or bass pickups prior to effects processing. IC Role / Device Role / Timing Role: JFET-input replacement or discrete alternative in ultra-high-impedance front-end. Use Value: hFE2 ≥ 600 enables >1 MΩ effective input impedance via base bias network; low NL avoids string-harmonic masking.

Microphone Preamp

Phono Stage Amplifier

Use Scenario: Amplifying low-level signals from dynamic or condenser microphones before ADC or tone control.

IC Role / Device Role / Timing Role: Discrete NPN transconductance amplifier in first gain stage with emitter degeneration.

Use Value: 25–40 mV noise level preserves signal integrity; hFE2 ≥ 600 ensures stable gain without feedback instability.

Use Scenario: RIAA-equalized amplification of vinyl playback cartridge outputs (typically 5 mV RMS).

IC Role / Device Role / Timing Role: High-input-impedance common-emitter amplifier with precise DC biasing.

Use Value: V_CEO = 120 V accommodates RIAA network voltage swings; low Cob (1.6–2.5 pF) avoids high-frequency roll-off.

Headphone Driver Buffer

Instrument Input Stage

Use Scenario: Low-distortion unity-gain buffer driving 16–32 Ω headphones from line-level sources.

IC Role / Device Role / Timing Role: Emitter-follower output stage with local negative feedback.

Use Value: V_CE(sat) ≤ 0.3 V ensures ≥ 2 V peak output swing into 32 Ω; P_C = 300 mW prevents thermal shutdown during sustained bass transients.

Use Scenario: High-Z input conditioning for electric guitar or bass pickups prior to effects processing.

IC Role / Device Role / Timing Role: JFET-input replacement or discrete alternative in ultra-high-impedance front-end.

Use Value: hFE2 ≥ 600 enables >1 MΩ effective input impedance via base bias network; low NL avoids string-harmonic masking.

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
2SC2240-GR	hFE = 200–400 (lower gain), f_T = 180 MHz (higher bandwidth), V_CEO = 120 V, same TO-92 package	Suitable for RF-adjacent audio filters but requires higher base drive due to lower hFE	Select when wider bandwidth is prioritized over gain stability in treble-enhancement circuits
KSC1845-Y	hFE = 300–600 (mid-range), NL = 30–50 mV (higher noise), V_CEO = 120 V, TO-92S package	Acceptable for non-critical line-level buffering but not recommended for phono or mic preamp front-ends	Choose for cost-sensitive consumer audio where SNR > 75 dB suffices and gain consistency is secondary

Compared with 2SC2240-GR and KSC1845-Y, the KSC2784PBU delivers superior noise performance and highest hFE uniformity in its class, making it the preferred choice for high-SNR, low-distortion audio gain stages where gain stability and thermal robustness are design-critical.

Availability

KSC2784PBU is available at Aetrix Electronics and suitable for microphone preamplifiers, phono stage amplifiers, headphone driver buffers, and instrument input stages requiring stable component supply and consistent low-noise transistor performance.

Supply support for KSC2784PBU 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 semiconductor manufacturer specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The KSC2784PBU belongs to Fairchild's legacy audio-frequency transistor family, designed specifically for low-noise, high-gain analog signal amplification in consumer and professional audio equipment.

FAQ

What is the maximum collector current rating for the KSC2784PBU?

The KSC2784PBU has an absolute maximum collector current (I_C) rating of 50 mA at T_a = 25°C. This rating assumes adequate heat sinking and derating per the SOA curve; continuous operation above 30 mA in TO-92S requires ambient temperature ≤ 50°C to maintain junction temperature below 150°C. The KSC2784PBU is not intended for switching or power amplification beyond this linear-region limit.

Does the KSC2784PBU have a documented complementary PNP part?

Yes, the KSC2784PBU is explicitly documented as complementary to the KSA1174 PNP transistor in Fairchild's original datasheet. Both share matched voltage ratings (V_CEO = 120 V), similar hFE ranges, and TO-92S packaging - enabling direct use in push-pull, differential pair, or quasi-complementary output stages without circuit redesign. The KSC2784PBU and KSA1174 were jointly characterized for audio applications.

What is the typical noise level of the KSC2784PBU and how is it measured?

The KSC2784PBU exhibits a noise level (NL) of 25–40 mV, measured under standard conditions: V_CE = 6 V, I_C = 1 mA, f = 20 Hz–20 kHz bandwidth, with RMS detection. This specification reflects wideband input-referred noise voltage relevant to audio preamp design. The KSC2784PBU's low NL directly contributes to high signal-to-noise ratio in microphone and phono applications where source impedances are ≤ 10 kΩ.

Can the KSC2784PBU be used in surface-mount assemblies?

No, the KSC2784PBU is packaged exclusively in the through-hole TO-92S configuration and lacks surface-mount variants. Its lead pitch (1.27 mm) and body dimensions are incompatible with standard SMT reflow profiles. For automated assembly, designers must use wave soldering or hand-soldering; no official SMD footprint or thermal profile is defined for the KSC2784PBU by Fairchild or ON Semiconductor.

What does the 'PBU' suffix indicate in KSC2784PBU?

Within Fairchild's historical part numbering, the 'PBU' suffix denotes the hFE2 classification band (600–1200) and TO-92S package variant. 'P' specifies the hFE2 range, 'B' indicates tape-and-reel packaging (though obsolete), and 'U' confirms the TO-92S outline. The KSC2784PBU is therefore the highest-gain, small-outline version of the KSC2784 family, distinct from 'F', 'E', or plain 'KSC2784' variants with lower hFE bands.

KSC2784PBU Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

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

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:: 200 @ 1mA, 6V

Power - Max:: 300 mW

Frequency - Transition:: 110MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92S

KSC2784PBU FAQ

1.How can I place an order for KSC2784PBU through Aetrix?

Please submit a Request for Quotation (RFQ) for KSC2784PBU 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 KSC2784PBU reliable?

The price and inventory of KSC2784PBU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for KSC2784PBU is usually 5 days.

3.What payment methods are accepted for KSC2784PBU?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for KSC2784PBU transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for KSC2784PBU?

KSC2784PBU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your KSC2784PBU 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 KSC2784PBU?

For technical support, including KSC2784PBU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your KSC2784PBU requirements.

6.How does Aetrix verify that KSC2784PBU is sourced from the original manufacturer or authorized distributors?

All KSC2784PBU 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 KSC2784PBU meets industry standards.

7.What is the process for return or replacement of KSC2784PBU?

All KSC2784PBU units undergo pre-shipment inspection (PSI). If there is an issue with KSC2784PBU, 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 KSC2784PBU part is unused and in its original packaging.

Return procedure for KSC2784PBU:

1.Submit a request within 90 days.

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

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