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

STMicroelectronics BC394

Name: BC394
Brand: STMicroelectronics
SKU: BC394
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC394

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-206AA, TO-18-3 Metal Can

Datasheet:: BC394.pdf

Description:: TRANS NPN 180V 0.1A TO-18

Quantity:: RFQ Add To RFQ list

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Inventory:3,595

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Product details

Overview

BC394 from STMicroelectronics is a silicon planar epitaxial NPN bipolar junction transistor in TO-18 metal package, rated for 180 V V_CEO and 180 V V_CBO, with 100 mA I_C, 0.4 W P_tot at T_amb ≤ 25 °C, and h_FE = 30–100 at I_C = 1–10 mA - designed for high-voltage video amplifier stages and pulse amplification in legacy broadcast and test equipment.

For engineers reviewing the BC394 datasheet, BC394 pinout, BC394 application, or BC394 equivalent, key selection considerations include its 180 V breakdown rating, TO-18 thermal resistance (R_thj-case = 107.1 °C/W), saturation voltage (V_CE(sat) = 0.2–0.4 V), transition frequency (f_T ≈ 100 MHz), and suitability for linear high-voltage gain stages where ruggedness and low leakage (I_CBO ≤ 50 nA) are required.

Technical Context

The BC394 operates as a medium-power, high-voltage NPN amplifier with DC current gain spanning 30 to 100 across collector currents from 1 mA to 10 mA at V_CE = 10 V. Its 180 V collector-base and collector-emitter breakdown voltages enable use in flyback driver and video output stage applications where transient overvoltage tolerance is critical.

Thermal design relies on its TO-18 metal case: R_thj-case = 107.1 °C/W enables direct heatsinking, while R_thj-amb = 375 °C/W limits ambient operation without forced cooling. The device exhibits low base-emitter saturation voltage (0.75–0.9 V) and minimal collector-base capacitance (5 pF at V_CB = 10 V, f = 1 MHz), supporting stable high-frequency gain.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	180 V - supports operation in high-voltage analog stages up to 180 V collector supply without breakdown
I_C	100 mA - delivers sufficient drive current for video line drivers and pulse amplifiers
P_tot (T_amb ≤ 25 °C)	0.4 W - defines maximum continuous power dissipation without heatsink in free-air conditions
h_FE	30–100 - provides predictable DC gain across 1–10 mA bias range for stable biasing in Class-A amplifiers
f_T	≈100 MHz - enables broadband video signal amplification up to ~30 MHz usable bandwidth
V_CE(sat)	0.2–0.4 V - ensures low conduction loss and minimal voltage drop in switching or saturated-mode applications
I_CBO	≤50 nA @ V_CB = 100 V - guarantees low leakage in high-impedance, high-voltage bias networks

Pinout & Package

BC394 is housed in a hermetically sealed TO-18 metal can package with three axial leads: Emitter (shortest lead), Base (center lead), Collector (longest lead, electrically connected to case). The metal case serves as the collector terminal and must be electrically isolated from heatsink unless intended as common-collector node.

Pin/Terminal	Circuit Role	Design Meaning
Collector (Case)	Main current sink and thermal path	Electrically tied to metal can; requires insulating washer if mounted to grounded heatsink
Base	Control electrode for current amplification	Receives small input current to modulate 30–100× larger collector current
Emitter	Current source reference terminal	Provides low-impedance return path; often tied to ground or negative rail in common-emitter configuration

Key Features

Feature	Design Value
High-voltage capability	180 V V_CEO/V_CBO enables safe operation in CRT deflection, flyback, and industrial HV supply circuits
Low leakage current	I_CBO ≤ 50 nA at 100 V ensures stable bias in high-impedance video coupling networks
TO-18 metal package	Robust hermetic seal and 107.1 °C/W R_thj-case support reliable thermal management in legacy equipment
Medium-frequency response	f_T ≈ 100 MHz allows faithful amplification of composite video signals (up to ~30 MHz bandwidth)
Saturation performance	V_CE(sat) ≤ 0.4 V at I_C = 50 mA reduces power loss in pulsed output stages

Applications

Video Output Amplifier

Flyback Pulse Driver

Use Scenario: Amplifying composite video signals in analog broadcast monitors and test pattern generators.

IC Role / Device Role / Timing Role: NPN Class-A linear amplifier operating at 12–24 V supply, driving 75 Ω coaxial load.

Use Value: 180 V rating prevents breakdown during sync pulse transients; 5 pF C_CBO minimizes high-frequency phase shift.

Use Scenario: Driving horizontal deflection yoke and flyback transformer primary in CRT-based oscilloscopes.

IC Role / Device Role / Timing Role: Switching amplifier in quasi-resonant flyback topology, handling repetitive 15.625 kHz pulses.

Use Value: 180 V V_CEO withstands flyback voltage spikes; 100 mA I_C supports peak current demands without secondary breakdown.

High-Voltage Sensor Interface

Legacy Industrial Signal Conditioning

Use Scenario: Level-shifting and buffering high-impedance sensor outputs (e.g., photomultiplier anode signals) referenced to +100 V rails.

IC Role / Device Role / Timing Role: Common-emitter buffer with emitter-follower input stage, isolating sensitive front-end from noisy power domains.

Use Value: 180 V V_CBO ensures safe operation at elevated collector potentials; low I_CBO preserves signal integrity.

Use Scenario: Amplifying low-level analog signals in discontinued PLC I/O modules and process controller analog cards.

IC Role / Device Role / Timing Role: DC-coupled gain stage in 0–10 V or 4–20 mA transmitter circuitry.

Use Value: Stable h_FE (30–100) enables repeatable calibration; TO-18 package ensures long-term reliability in industrial enclosures.

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage NPN amplifier applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC395	Same TO-18 package; higher h_FE (60–120), identical 180 V ratings and 100 mA I_C	Better suited for low-input-current amplifier designs requiring higher gain stability	Select BC395 when circuit bias sensitivity demands tighter h_FE control; otherwise BC394 remains optimal for cost-sensitive legacy repair
2N3904	TO-92 plastic package; lower V_CEO (40 V), higher f_T (300 MHz), but only 200 mW P_tot	Restricted to low-voltage logic interface and general-purpose switching - not suitable for >60 V operation	Use only in new low-voltage designs; not a functional replacement for BC394's high-voltage role

Compared with BC395 and 2N3904, the BC394 uniquely balances 180 V ruggedness, TO-18 thermal robustness, and moderate gain - making it irreplaceable in legacy high-voltage analog systems where voltage margin and hermetic reliability outweigh raw speed or gain.

Availability

BC394 is available at Aetrix Electronics and suitable for video output amplifier, flyback pulse driver, and high-voltage sensor interface applications requiring stable component supply and long-lifecycle support for legacy system maintenance.

Supply support for BC394 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The BC394 belongs to ST's legacy bipolar transistor product line, developed specifically for high-reliability analog signal conditioning and high-voltage amplification in broadcast, test, and industrial instrumentation equipment.

FAQ

Is BC394 still in active production?

No - BC394 is marked "Obsolete Product(s)" in the official STMicroelectronics datasheet (December 2002 revision). It is no longer manufactured, but Aetrix Electronics maintains verified legacy stock with full traceability and extended availability support for repair and maintenance programs.

Can BC394 be used as a direct replacement for BC337 in a 12 V amplifier circuit?

No - BC337 has V_CEO = 45 V and TO-92 packaging, while BC394 is rated for 180 V and uses TO-18. Substituting BC394 introduces mechanical incompatibility (lead spacing, mounting), excessive gain variation, and unnecessary voltage overhead - potentially destabilizing bias networks calibrated for BC337's lower h_FE and thermal profile.

What is the maximum safe operating temperature for BC394?

The BC394 has a maximum junction temperature (T_j) of 175 °C and storage temperature range of –55 °C to +175 °C. For continuous operation, case temperature must remain ≤25 °C to maintain rated 0.4 W dissipation; derating is required above that - e.g., 0.2 W at T_C = 75 °C per the 107.1 °C/W R_thj-case.

Does BC394 require a heatsink in typical video amplifier use?

In standard video output stages dissipating ≤300 mW, the TO-18 metal case provides sufficient thermal conduction without an external heatsink - especially when mounted to a grounded chassis. However, sustained operation near 0.4 W or in enclosed, high-ambient environments (>40 °C) requires thermal interface material and a dedicated heatsink to limit T_j below 175 °C.

BC394 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-206AA, TO-18-3 Metal Can

Packaging:: Bulk

Product Status:: Obsolete

Transistor Type:: NPN

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

Voltage - Collector Emitter Breakdown (Max):: 180 V

Vce Saturation (Max) @ Ib, Ic:: 400mV @ 5mA, 50mA

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

DC Current Gain (hFE) (Min) @ Ic, Vce:: 30 @ 10mA, 10V

Power - Max:: 400 mW

Frequency - Transition:: -

Operating Temperature:: 175°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-18

BC394 FAQ

1.How can I place an order for BC394 through Aetrix?

Please submit a Request for Quotation (RFQ) for BC394 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 BC394 reliable?

The price and inventory of BC394 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC394 is usually 5 days.

3.What payment methods are accepted for BC394?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC394 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC394?

BC394 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC394 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 BC394?

For technical support, including BC394 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC394 requirements.

6.How does Aetrix verify that BC394 is sourced from the original manufacturer or authorized distributors?

All BC394 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 BC394 meets industry standards.

7.What is the process for return or replacement of BC394?

All BC394 units undergo pre-shipment inspection (PSI). If there is an issue with BC394, 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 BC394 part is unused and in its original packaging.

Return procedure for BC394:

1.Submit a request within 90 days.

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

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