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 BC239CG

Name: BC239CG
Brand: onsemi
SKU: BC239CG
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: BC239CG

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BC239CG.pdf

Description:: TRANS NPN 25V 0.1A TO92

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:3,974

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

Product details

Overview

BC239CG from onsemi is an NPN silicon general-purpose amplifier transistor in TO-92 package, rated for V_CEO = 25 V, I_C = 100 mA, P_D = 350 mW at T_A = 25°C, with h_FE = 120–500 (at I_C = 10 mA), and f_T = 150 MHz - used in low-noise audio preamplifier stages and signal switching circuits.

For engineers reviewing the BC239CG datasheet, pinout, applications, or equivalent options, key selection considerations include its 25 V V_CEO, 5.0 V V_EBO, 2.0 dB noise figure at 1 kHz, 4.5 pF C_obo, and Pb-free TO-92 packaging for lead-free assembly compliance.

Technical Context

The BC239CG operates as a discrete NPN bipolar junction transistor optimized for linear amplification and low-current switching. Its DC current gain spans 120–500 depending on bias point (I_C = 10 mA to 100 mA), and it delivers 150 MHz f_T under standard test conditions (I_C = 0.5 mA, V_CE = 3.0 V).

Thermal performance is defined by R_JA = 357°C/W and R_JC = 125°C/W, supporting operation from −55°C to +150°C. It exhibits low saturation voltage (V_CE(sat) = 0.07 V typ. at I_C/I_B = 10) and low noise (NF = 2.0 dB at I_C = 0.2 mA, R_S = 2 kΩ, f = 1 kHz), making it suitable for high-fidelity analog front-ends.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	25 V - maximum collector-emitter voltage before breakdown; sets safe operating range for low-voltage amplifier rails.
I_C (max)	100 mA - continuous collector current limit; defines usable output drive capability in small-signal stages.
P_D @ 25°C	350 mW - thermal power dissipation limit at ambient; requires heatsinking or derating above 25°C (2.8 mW/°C).
h_FE	120–500 - DC current gain range across I_C = 10–100 mA; enables stable bias design in Class-A amplifiers.
f_T	150 MHz - unity-gain bandwidth; supports RF amplification up to ~50 MHz with adequate gain margin.
NF	2.0 dB @ 1 kHz - low-noise figure at low collector current; critical for microphone preamp and sensor interface stages.
C_obo	4.5 pF - collector-base capacitance at V_CB = 10 V; limits high-frequency stability and Miller effect in common-emitter designs.

Pinout & Package

BC239CG uses the industry-standard TO-92 (Case 29-11, Style 17) plastic package with axial leads and Pb-free finish. Dimensions conform to ANSI Y14.5M, with body height ~4.5 mm and lead pitch 2.54 mm.

Pin/Terminal	Circuit Role	Design Meaning
1	Collector	Main current output terminal; connects to load or next stage input; carries full I_C and dissipates most power.
2	Base	Control electrode; small I_B regulates I_C; requires proper bias network for stable Q-point.
3	Emitter	Current return path; often grounded or connected to emitter resistor for DC stabilization and AC feedback.

Key Features

Feature	Design Value
Low noise figure	2.0 dB at 1 kHz enables high-SNR audio preamplification without added noise degradation.
Pb-free TO-92 package	RoHS-compliant construction with verified solderability per ON Semiconductor Soldering Manual.
Wide h_FE range	120–500 supports consistent gain across production lots when paired with emitter degeneration.
High f_T	150 MHz allows use in VHF oscillator and broadband amplifier designs up to 50 MHz.
Low V_CE(sat)	0.07 V typical at I_C/I_B = 10 reduces conduction loss in switching applications.

Applications

Audio Preamp Stage	Signal Switching Circuit
Use Scenario: Amplifying weak signals from electret microphones or piezoelectric sensors in portable audio devices. IC Role / Device Role / Timing Role: Discrete NPN transconductance amplifier providing 20–40 dB voltage gain with minimal added noise. Use Value: 2.0 dB NF and h_FE ≥ 120 ensure clean signal amplification without requiring complex bias compensation.	Use Scenario: Enabling/disabling analog signal paths in battery-powered instrumentation multiplexers. IC Role / Device Role / Timing Role: Low-power saturated switch controlling signal routing between sensor inputs and ADC front-end. Use Value: V_CE(sat) ≤ 0.2 V and fast turn-on support <1 µs switching with negligible voltage drop.
RF Oscillator Core	DC Bias Reference Generator
Use Scenario: Active device in Colpitts or Clapp oscillator topologies generating 10–30 MHz clock references. IC Role / Device Role / Timing Role: High-f_T NPN sustaining oscillation via tuned LC tank feedback. Use Value: 150 MHz f_T and 4.5 pF C_obo enable stable oscillation with predictable phase noise below −100 dBc/Hz.	Use Scenario: Building precision current sources or voltage references in analog power management ICs. IC Role / Device Role / Timing Role: Matched transistor pair element in bandgap reference or current mirror subcircuits. Use Value: Tight h_FE distribution and low base spreading resistance (r_b ≈ 150 Ω) improve matching accuracy in bias networks.

Audio Preamp Stage

Signal Switching Circuit

Use Scenario: Amplifying weak signals from electret microphones or piezoelectric sensors in portable audio devices.

IC Role / Device Role / Timing Role: Discrete NPN transconductance amplifier providing 20–40 dB voltage gain with minimal added noise.

Use Value: 2.0 dB NF and h_FE ≥ 120 ensure clean signal amplification without requiring complex bias compensation.

Use Scenario: Enabling/disabling analog signal paths in battery-powered instrumentation multiplexers.

IC Role / Device Role / Timing Role: Low-power saturated switch controlling signal routing between sensor inputs and ADC front-end.

Use Value: V_CE(sat) ≤ 0.2 V and fast turn-on support <1 µs switching with negligible voltage drop.

RF Oscillator Core

DC Bias Reference Generator

Use Scenario: Active device in Colpitts or Clapp oscillator topologies generating 10–30 MHz clock references.

IC Role / Device Role / Timing Role: High-f_T NPN sustaining oscillation via tuned LC tank feedback.

Use Value: 150 MHz f_T and 4.5 pF C_obo enable stable oscillation with predictable phase noise below −100 dBc/Hz.

Use Scenario: Building precision current sources or voltage references in analog power management ICs.

IC Role / Device Role / Timing Role: Matched transistor pair element in bandgap reference or current mirror subcircuits.

Use Value: Tight h_FE distribution and low base spreading resistance (r_b ≈ 150 Ω) improve matching accuracy in bias networks.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN amplifier transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC239C	Same die, SnPb lead finish; no Pb-free certification; identical electrical specs and TO-92 mechanical form.	Not suitable for RoHS-compliant production; acceptable for prototyping or legacy repair where Pb-free is not mandated.	Select BC239C only if Pb-free compliance is not required and cost sensitivity outweighs environmental compliance needs.
BC547C	V_CEO = 45 V (vs. 25 V); h_FE = 420–800; f_T = 300 MHz; same TO-92 package but higher voltage rating and gain spread.	Better suited for higher-voltage amplifier stages or faster switching; may require re-biasing due to higher h_FE.	Choose BC547C when system rail exceeds 25 V or when >150 MHz bandwidth is needed; verify thermal margin at 500 mW P_D.

Compared with BC239C and BC547C, the BC239CG offers guaranteed Pb-free compliance with identical low-noise, medium-speed performance - ideal for cost-sensitive, RoHS-mandated audio and sensor signal conditioning where 25 V operation suffices.

Availability

BC239CG is available at Aetrix Electronics and suitable for audio preamplifier stages, analog signal switching circuits, RF oscillator cores, and DC bias reference generators requiring stable component supply and RoHS-compliant manufacturing.

Supply support for BC239CG 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 focused on energy-efficient electronics, delivering power management, analog, sensor, and logic solutions for automotive, industrial, and consumer markets.

The BC239CG belongs to onsemi's legacy general-purpose bipolar transistor product line, designed specifically for cost-effective, reliable linear amplification and low-current switching in space-constrained through-hole applications.

FAQ

What is the maximum collector-emitter voltage rating for BC239CG?

The BC239CG has a maximum collector-emitter voltage (V_CEO) rating of 25 Vdc. This value is specified under test condition I_C = 2.0 mA and I_B = 0, and represents the absolute maximum voltage that can be applied between collector and emitter before breakdown occurs. Exceeding this rating risks permanent device damage. The BC239CG must be operated within this limit in all circuit configurations, including transient conditions.

Does BC239CG have Pb-free construction?

Yes, BC239CG is explicitly manufactured with Pb-free terminations and complies with RoHS Directive 2011/65/EU. The "G" suffix denotes Pb-free packaging, confirmed in the ON Semiconductor BC237/D datasheet Rev. 4 (2006) and supported by onsemi's Pb-Free Packaging Implementation documentation. This ensures compatibility with lead-free reflow soldering profiles and eliminates hazardous substance concerns in final assembly.

What is the typical noise figure of BC239CG and under what conditions is it measured?

The BC239CG has a typical noise figure (NF) of 2.0 dB, measured at I_C = 0.2 mA, V_CE = 5.0 V, source resistance R_S = 2.0 kΩ, and frequency f = 1.0 kHz. This low-noise performance is validated in the official BC237/D datasheet and makes the BC239CG especially suitable for microphone preamplifiers and other low-level analog signal amplification tasks where signal integrity is critical.

Can BC239CG be used as a direct replacement for BC239C in existing designs?

BC239CG is a Pb-free version of BC239C with identical electrical specifications, pinout, and TO-92 mechanical dimensions. While not labeled "drop-in" in official documentation, the BC239CG shares all key parameters - including V_CEO, h_FE, f_T, and thermal resistance - with BC239C. Therefore, BC239CG can replace BC239C in most designs without circuit modification, provided lead-free soldering processes are used and thermal margins are verified.

What is the thermal resistance junction-to-ambient (R_JA) for BC239CG?

The thermal resistance junction-to-ambient (R_JA) for BC239CG is 357°C/W, as specified in the BC237/D datasheet under "THERMAL CHARACTERISTICS." This value assumes free-air convection mounting on a standard PCB with no heatsink. Designers must apply appropriate derating - 2.8 mW/°C above 25°C ambient - to maintain junction temperature below the maximum rated 150°C during continuous operation.

BC239CG 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:: NPN

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

Voltage - Collector Emitter Breakdown (Max):: 25 V

Vce Saturation (Max) @ Ib, Ic:: 600mV @ 5mA, 100mA

Current - Collector Cutoff (Max):: 15nA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 380 @ 2mA, 5V

Power - Max:: 350 mW

Frequency - Transition:: 280MHz

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

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92 (TO-226)

BC239CG FAQ

1.How can I place an order for BC239CG through Aetrix?

Please submit a Request for Quotation (RFQ) for BC239CG 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 BC239CG reliable?

The price and inventory of BC239CG are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC239CG is usually 5 days.

3.What payment methods are accepted for BC239CG?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC239CG transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC239CG?

BC239CG orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC239CG 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 BC239CG?

For technical support, including BC239CG datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC239CG requirements.

6.How does Aetrix verify that BC239CG is sourced from the original manufacturer or authorized distributors?

All BC239CG 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 BC239CG meets industry standards.

7.What is the process for return or replacement of BC239CG?

All BC239CG units undergo pre-shipment inspection (PSI). If there is an issue with BC239CG, 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 BC239CG part is unused and in its original packaging.

Return procedure for BC239CG:

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…