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

onsemi KSC2784FTA

Name: KSC2784FTA
Brand: onsemi
SKU: KSC2784FTA
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: KSC2784FTA

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: KSC2784FTA.pdf

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

Quantity:: RFQ Add To RFQ list

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Product details

Overview

KSC2784FTA from ON Semiconductor (formerly Fairchild) 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, f_T = 50–110 MHz, and h_FE2 = 600–1200 at I_C = 1 mA - deployed in preamplifier stages of consumer audio equipment.

For engineers reviewing the KSC2784FTA datasheet, pinout, applications, or equivalent options, key selection criteria include low noise level (25–40 mV), high DC current gain, TO-92S package compatibility, V_CE(sat) ≤ 0.3 V at I_C = 10 mA/I_B = 1 mA, and complementarity to KSA1174 for push-pull designs.

Technical Context

This NPN transistor operates in linear active mode for analog signal amplification, featuring a high h_FE2 classification (U-grade: 600–1200) and low Cob (1.6–2.5 pF at V_CB = 30 V), enabling stable gain up to ~100 MHz. Its f_T variation with I_C supports wideband audio fidelity without peaking artifacts.

The device uses epitaxial base construction to minimize 1/f noise and achieve NL = 25–40 mV (typical), meeting requirements for microphone preamps and phono-stage inputs. V_BE(on) = 0.55–0.65 V at I_C = 1 mA ensures predictable biasing in Class-A amplifier topologies.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	120 V - supports rail voltages up to ±60 V in dual-supply audio circuits without breakdown.
I_C	50 mA - sufficient for low-power line-level and preamp stage collector loads.
f_T	50–110 MHz - enables flat frequency response beyond 20 kHz with margin for stability compensation.
h_FE2	600–1200 - ensures high open-loop gain and low input-referred noise in common-emitter configurations.
NL	25–40 mV - meets low-noise requirement for microphone and moving-coil cartridge amplification.
V_CE(sat)	0.07–0.3 V - minimizes voltage drop and power loss in saturated-switch applications like muting circuits.
C_ob	1.6–2.5 pF - reduces Miller effect and preserves bandwidth in high-gain CE stages.

Pinout & Package

Package: TO-92S (3-lead, small-outline plastic through-hole), lead spacing 1.27 mm, body height 3.72 mm, footprint compatible with standard PCB mounting fixtures for discrete transistor assembly.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current sink terminal	Connected to ground or bias network; low-impedance return path for amplified signal current.
2 (Collector)	Current source terminal	Drives load impedance (e.g., next stage input or RC coupling network); high-voltage tolerance enables direct coupling to supply rails.
3 (Base)	Control input terminal	Accepts bias current to set operating point; high h_FE allows minimal base drive for low-noise operation.

Key Features

Feature	Design Value
Low noise level	NL = 25–40 mV - directly enables high-SNR preamplification of weak audio signals (e.g., electret mics).
High DC current gain	h_FE2 = 600–1200 - reduces required base bias current and improves input impedance matching.
Complementary pairing	Designed as NPN counterpart to KSA1174 (PNP) - supports matched push-pull output stages with symmetrical distortion profiles.
High f_T / low C_ob ratio	f_T ≥ 50 MHz, C_ob ≤ 2.5 pF - maintains gain-bandwidth product > 100 MHz·pF, critical for wideband audio fidelity.

Applications

Microphone Preamplifier	Phono Preamp Stage
Use Scenario: Amplifying low-level signals from condenser or electret microphones with gain > 40 dB and SNR > 70 dB. IC Role / Device Role / Timing Role: NPN transconductance amplifier in common-emitter configuration with emitter degeneration. Use Value: Low NL (25–40 mV) and high h_FE2 (600–1200) enable clean amplification without added op-amp noise floor penalties.	Use Scenario: RIAA-equalized amplification of moving-magnet cartridge outputs (2–5 mV, 47 kΩ source). IC Role / Device Role / Timing Role: First-stage discrete gain block with passive RIAA network feedback. Use Value: V_CEO = 120 V supports ±15 V rails; low C_ob (1.6–2.5 pF) prevents high-frequency roll-off in 20 kHz+ response.
Audio Tone Control	Muting Switch Circuit
Use Scenario: Discrete Baxandall-style tone stack driver requiring linear gain control over bass/mid/treble bands. IC Role / Device Role / Timing Role: High-linearity active element in shunt-feedback gain cell with adjustable emitter resistor. Use Value: Stable h_FE across I_C = 0.1–10 mA ensures consistent Q-factor and frequency response under varying bias conditions.	Use Scenario: Solid-state mute switch in headphone amplifiers or mixer channel inserts. IC Role / Device Role / Timing Role: Saturated NPN switch controlling signal path continuity via collector-emitter short. Use Value: V_CE(sat) ≤ 0.3 V at I_C/I_B = 10/1 mA ensures < 10 mΩ on-resistance, minimizing insertion loss and THD.

Microphone Preamplifier

Phono Preamp Stage

Use Scenario: Amplifying low-level signals from condenser or electret microphones with gain > 40 dB and SNR > 70 dB.

IC Role / Device Role / Timing Role: NPN transconductance amplifier in common-emitter configuration with emitter degeneration.

Use Value: Low NL (25–40 mV) and high h_FE2 (600–1200) enable clean amplification without added op-amp noise floor penalties.

Use Scenario: RIAA-equalized amplification of moving-magnet cartridge outputs (2–5 mV, 47 kΩ source).

IC Role / Device Role / Timing Role: First-stage discrete gain block with passive RIAA network feedback.

Use Value: V_CEO = 120 V supports ±15 V rails; low C_ob (1.6–2.5 pF) prevents high-frequency roll-off in 20 kHz+ response.

Audio Tone Control

Muting Switch Circuit

Use Scenario: Discrete Baxandall-style tone stack driver requiring linear gain control over bass/mid/treble bands.

IC Role / Device Role / Timing Role: High-linearity active element in shunt-feedback gain cell with adjustable emitter resistor.

Use Value: Stable h_FE across I_C = 0.1–10 mA ensures consistent Q-factor and frequency response under varying bias conditions.

Use Scenario: Solid-state mute switch in headphone amplifiers or mixer channel inserts.

IC Role / Device Role / Timing Role: Saturated NPN switch controlling signal path continuity via collector-emitter short.

Use Value: V_CE(sat) ≤ 0.3 V at I_C/I_B = 10/1 mA ensures < 10 mΩ on-resistance, minimizing insertion loss and THD.

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	h_FE = 300–600 (lower max gain), f_T = 180 MHz (higher), NL = 3 dB lower (≈20 mV)	Better HF extension but reduced midband gain stability; requires tighter bias control.	Prefer when ultra-wideband response > 500 kHz is prioritized over maximum low-frequency SNR.
KSC1845FTA	h_FE = 200–400 (P-grade), V_CEO = 160 V, P_C = 400 mW, NL = 30–50 mV	Higher voltage rating and power handling, but higher noise and lower gain limit dynamic range in mic preamps.	Select for higher-voltage line drivers or where thermal margin > 300 mW is required in continuous operation.

Compared with 2SC2240-GR and KSC1845FTA, the KSC2784FTA delivers superior noise-to-gain ratio (25–40 mV NL with h_FE2 = 600–1200), making it optimal for low-level audio amplification where SNR dominates design trade-offs.

Availability

KSC2784FTA is available at Aetrix Electronics and suitable for microphone preamplifiers, phono equalization stages, and audio tone control circuits requiring stable component supply, consistent h_FE binning, and low-noise performance across production batches.

Supply support for KSC2784FTA 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

ON Semiconductor (acquired Fairchild Semiconductor in 2016) designs high-performance analog and discrete semiconductors for automotive, industrial, and consumer applications.

The KSC2784FTA belongs to Fairchild's legacy audio transistor family, engineered specifically for low-noise, high-gain analog signal conditioning in consumer audio systems.

FAQ

What is the maximum collector-emitter voltage rating for KSC2784FTA?

The KSC2784FTA has a maximum collector-emitter voltage (V_CEO) rating of 120 V at T_a = 25°C. This rating remains valid up to T_J = 150°C per derating curves in the original Fairchild datasheet Rev. A2. Exceeding this voltage risks avalanche breakdown and permanent device failure. The KSC2784FTA must be operated within this absolute maximum limit in all circuit configurations.

Is KSC2784FTA pin-compatible with KSA1174?

No, the KSC2784FTA (NPN) and KSA1174 (PNP) are complementary devices but not pin-compatible - the KSC2784FTA pinout is E-C-B (1-2-3), while the KSA1174 uses E-C-B in reverse order (C-E-B or B-C-E depending on variant). Their electrical symmetry supports push-pull design, but PCB layout requires separate footprints. The KSC2784FTA datasheet explicitly states "Complement to KSA1174", not pin-for-pin replacement.

What is the typical noise level of KSC2784FTA and how is it measured?

The KSC2784FTA exhibits a noise level (NL) of 25–40 mV, measured per the original Fairchild test method: 1 kHz bandwidth, I_C = 1 mA, V_CE = 6 V, with emitter degeneration and no external filtering. This value reflects input-referred noise voltage in common-emitter configuration and directly impacts SNR in microphone preamplifier applications. The KSC2784FTA's low NL stems from its epitaxial base structure and tight h_FE binning.

Does KSC2784FTA support audio frequencies up to 20 kHz with flat gain response?

Yes, the KSC2784FTA supports flat gain response up to at least 20 kHz due to its f_T = 50–110 MHz and low C_ob = 1.6–2.5 pF. In properly compensated common-emitter stages with moderate gain (A_v ≤ 100), phase margin exceeds 45° across the audio band. The KSC2784FTA's gain-bandwidth product and low Miller capacitance ensure minimal high-frequency roll-off in real-world audio amplifier designs.

What is the package type and lead configuration of KSC2784FTA?

The KSC2784FTA uses the TO-92S package: a 3-lead, small-outline plastic through-hole case with lead spacing of 1.27 mm and body height of 3.72 mm. Pin 1 is Emitter, Pin 2 is Collector, Pin 3 is Base - confirmed by the mechanical drawing in the Fairchild KSC2784 Rev. A2 datasheet. The TO-92S footprint is mechanically distinct from standard TO-92 and requires dedicated stencil or placement tooling.

KSC2784FTA Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

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

Packaging:: Tape & Box (TB)

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:: 300 @ 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

KSC2784FTA FAQ

1.How can I place an order for KSC2784FTA through Aetrix?

Please submit a Request for Quotation (RFQ) for KSC2784FTA 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 KSC2784FTA reliable?

The price and inventory of KSC2784FTA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for KSC2784FTA is usually 5 days.

3.What payment methods are accepted for KSC2784FTA?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for KSC2784FTA transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for KSC2784FTA?

KSC2784FTA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your KSC2784FTA 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 KSC2784FTA?

For technical support, including KSC2784FTA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your KSC2784FTA requirements.

6.How does Aetrix verify that KSC2784FTA is sourced from the original manufacturer or authorized distributors?

All KSC2784FTA 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 KSC2784FTA meets industry standards.

7.What is the process for return or replacement of KSC2784FTA?

All KSC2784FTA units undergo pre-shipment inspection (PSI). If there is an issue with KSC2784FTA, 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 KSC2784FTA part is unused and in its original packaging.

Return procedure for KSC2784FTA:

1.Submit a request within 90 days.

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

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