BF494 Transistor: Circuits, Pinout, and Datasheet
TRANSISTOR RF NPN 20V TO-92
BF494 is an NPN medium frequency transistor in a TO-92; SOT54 plastic package. This article mainly introduces circuits, pinout, datasheet and other detailed information about ON Semiconductor BF494.

Powerful FM oscilator with BF494
BF494 Description
BF494 is an NPN medium frequency transistor in a TO-92; SOT54 plastic package. A semiconductor device is used to amplify or switch electronic signals and electrical power. It's made of semiconductor material and has at least three terminals for connecting to a circuit outside of it. The current through another pair of terminals is controlled by a voltage or current applied to one pair of transistor terminals. A transistor can magnify a signal because the regulated (output) power can be higher than the controlling (input) power. Some transistors are still packaged separately nowadays, but many more are included in integrated circuits.
BF494 Pinout

Pinout
| Pin Number | Description |
| 1 | collector |
| 2 | emitter |
| 3 | base |
BF494 CAD Model

Symbol

Footprint

3D Model
BF494 Features
• Low current (max. 30 mA)
• Low voltage (max. 20 V).
• Advanced process technology
• Low error voltage
• Fast switching speed
• Full-voltage operation
• High power and current handling capability
Specifications
- TypeParameter
- Mount
In electronic components, the term "Mount" typically refers to the method or process of physically attaching or fixing a component onto a circuit board or other electronic device. This can involve soldering, adhesive bonding, or other techniques to secure the component in place. The mounting process is crucial for ensuring proper electrical connections and mechanical stability within the electronic system. Different components may have specific mounting requirements based on their size, shape, and function, and manufacturers provide guidelines for proper mounting procedures to ensure optimal performance and reliability of the electronic device.
Through Hole - Mounting Type
The "Mounting Type" in electronic components refers to the method used to attach or connect a component to a circuit board or other substrate, such as through-hole, surface-mount, or panel mount.
Through Hole - Package / Case
refers to the protective housing that encases an electronic component, providing mechanical support, electrical connections, and thermal management.
TO-226-3, TO-92-3 (TO-226AA) - Number of Pins3
- Collector-Emitter Breakdown Voltage20V
- Number of Elements1
- hFEMin65
- Operating Temperature
The operating temperature is the range of ambient temperature within which a power supply, or any other electrical equipment, operate in. This ranges from a minimum operating temperature, to a peak or maximum operating temperature, outside which, the power supply may fail.
150°C TJ - Packaging
Semiconductor package is a carrier / shell used to contain and cover one or more semiconductor components or integrated circuits. The material of the shell can be metal, plastic, glass or ceramic.
Bulk - Part Status
Parts can have many statuses as they progress through the configuration, analysis, review, and approval stages.
Obsolete - Moisture Sensitivity Level (MSL)
Moisture Sensitivity Level (MSL) is a standardized rating that indicates the susceptibility of electronic components, particularly semiconductors, to moisture-induced damage during storage and the soldering process, defining the allowable exposure time to ambient conditions before they require special handling or baking to prevent failures
1 (Unlimited) - ECCN Code
An ECCN (Export Control Classification Number) is an alphanumeric code used by the U.S. Bureau of Industry and Security to identify and categorize electronic components and other dual-use items that may require an export license based on their technical characteristics and potential for military use.
EAR99 - Voltage - Rated DC
Voltage - Rated DC is a parameter that specifies the maximum direct current (DC) voltage that an electronic component can safely handle without being damaged. This rating is crucial for ensuring the proper functioning and longevity of the component in a circuit. Exceeding the rated DC voltage can lead to overheating, breakdown, or even permanent damage to the component. It is important to carefully consider this parameter when designing or selecting components for a circuit to prevent any potential issues related to voltage overload.
20V - Max Power Dissipation
The maximum power that the MOSFET can dissipate continuously under the specified thermal conditions.
350mW - Reach Compliance Code
Reach Compliance Code refers to a designation indicating that electronic components meet the requirements set by the Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) regulation in the European Union. It signifies that the manufacturer has assessed and managed the chemical substances within the components to ensure safety and environmental protection. This code is vital for compliance with regulations aimed at minimizing risks associated with hazardous substances in electronic products.
unknown - Current Rating
Current rating is the maximum current that a fuse will carry for an indefinite period without too much deterioration of the fuse element.
30mA - Element Configuration
The distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals.
Single - Power Dissipation
the process by which an electronic or electrical device produces heat (energy loss or waste) as an undesirable derivative of its primary action.
350mW - Transistor Type
Transistor type refers to the classification of transistors based on their operation and construction. The two primary types are bipolar junction transistors (BJTs) and field-effect transistors (FETs). BJTs use current to control the flow of current, while FETs utilize voltage to control current flow. Each type has its own subtypes, such as NPN and PNP for BJTs, and MOSFETs and JFETs for FETs, impacting their applications and characteristics in electronic circuits.
NPN - Collector Emitter Voltage (VCEO)
Collector-Emitter Voltage (VCEO) is a key parameter in electronic components, particularly in transistors. It refers to the maximum voltage that can be applied between the collector and emitter terminals of a transistor while the base terminal is open or not conducting. Exceeding this voltage limit can lead to breakdown and potential damage to the transistor. VCEO is crucial for ensuring the safe and reliable operation of the transistor within its specified limits. Designers must carefully consider VCEO when selecting transistors for a circuit to prevent overvoltage conditions that could compromise the performance and longevity of the component.
20V - Max Collector Current
Max Collector Current is a parameter used to specify the maximum amount of current that can safely flow through the collector terminal of a transistor or other electronic component without causing damage. It is typically expressed in units of amperes (A) and is an important consideration when designing circuits to ensure that the component operates within its safe operating limits. Exceeding the specified max collector current can lead to overheating, degradation of performance, or even permanent damage to the component. Designers must carefully consider this parameter when selecting components and designing circuits to ensure reliable and safe operation.
30mA - DC Current Gain (hFE) (Min) @ Ic, Vce
The parameter "DC Current Gain (hFE) (Min) @ Ic, Vce" in electronic components refers to the minimum value of the DC current gain, denoted as hFE, under specific operating conditions of collector current (Ic) and collector-emitter voltage (Vce). The DC current gain hFE represents the ratio of the collector current to the base current in a bipolar junction transistor (BJT), indicating the amplification capability of the transistor. The minimum hFE value at a given Ic and Vce helps determine the transistor's performance and efficiency in amplifying signals within a circuit. Designers use this parameter to ensure proper transistor selection and performance in various electronic applications.
67 @ 1mA 10V - Collector Base Voltage (VCBO)
Collector Base Voltage (VCBO) is the maximum allowable voltage that can be applied between the collector and base terminals of a bipolar junction transistor when the emitter is open. It is a critical parameter that determines the voltage rating of the transistor and helps prevent breakdown in the collector-base junction. Exceeding this voltage can lead to permanent damage or failure of the component.
30V - Emitter Base Voltage (VEBO)
Emitter Base Voltage (VEBO) is a parameter used in electronic components, particularly in transistors. It refers to the maximum voltage that can be applied between the emitter and base terminals of a transistor without causing damage to the device. Exceeding this voltage limit can lead to breakdown of the transistor and potential failure. VEBO is an important specification to consider when designing circuits to ensure the proper operation and reliability of the components. It is typically provided in the datasheet of the transistor and should be carefully observed to prevent any potential damage during operation.
5V - RoHS Status
RoHS means “Restriction of Certain Hazardous Substances” in the “Hazardous Substances Directive” in electrical and electronic equipment.
RoHS Compliant - Lead Free
Lead Free is a term used to describe electronic components that do not contain lead as part of their composition. Lead is a toxic material that can have harmful effects on human health and the environment, so the electronics industry has been moving towards lead-free components to reduce these risks. Lead-free components are typically made using alternative materials such as silver, copper, and tin. Manufacturers must comply with regulations such as the Restriction of Hazardous Substances (RoHS) directive to ensure that their products are lead-free and environmentally friendly.
Lead Free
Parts with Similar Specs
- ImagePart NumberManufacturerMountPackage / CaseCollector Emitter Breakdown VoltageMax Collector CurrenthFE MinMax Power DissipationPower DissipationCollector Base Voltage (VCBO)View Compare
BF494
Through Hole
TO-226-3, TO-92-3 (TO-226AA)
20 V
30 mA
65
350 mW
350 mW
30 V
Through Hole
TO-226-3, TO-92-3 (TO-226AA)
25 V
50 mA
60
350 mW
350 mW
30 V
Through Hole
TO-226-3, TO-92-3 (TO-226AA)
20 V
30 mA
40
250 mW
250 mW
30 V
Through Hole
TO-226-3, TO-92-3 (TO-226AA)
25 V
50 mA
60
350 mW
350 mW
30 V
BF494 Circuit Diagram

Circuit Diagram
The circuit diagram for the simplest transistor-based FM transmitter is shown below. Because this is a basic design, great performance or range cannot be guaranteed. For FM modulation, a general-purpose radio frequency transistor (BF 494 (Q1) is employed. The sound is captured with a condenser microphone. The sound is converted to electrical changes via the condenser mic, and these differences are supplied to Q1 's base, which performs amplification and modulation. The frequency of transmission is determined by the capacitor C2 and the resistor L1. A 9V transistor radio battery can be used to power the circuit.
• Wind 8 turns of 1mm thick enamel coated copper wire on a ball pen refill to make coil L1. To connect the antenna, the coil should be tapped in the middle.
• An antenna can be made out of a 30 centimeter wire.
• Keep in mind! This circuit is a very basic one. There is no assurance of good performance or range. Only suitable for demo applications. I only got an 8-meter range with good sound quality.
• Battery is strictly recommended because mains powered supply may induce additional noise.
BF494 Alternatives
| Part Number | Description | Manufacturer |
| BF494-AMMOTRANSISTORS | TRANSISTOR 30 mA, 20 V, NPN, Si, SMALL SIGNAL TRANSISTOR, TO-92, BIP General Purpose Small Signal | NXP Semiconductors |
| BF494-T/RTRANSISTORS | TRANSISTOR 30 mA, 20 V, NPN, Si, SMALL SIGNAL TRANSISTOR, TO-92, BIP General Purpose Small Signal | NXP Semiconductors |
| BF494TRANSISTORS | TRANSISTOR NPN, Si, SMALL SIGNAL TRANSISTOR, TO-92, BIP General Purpose Small Signal | National Semiconductor Corporation |
BF494 Applications
• HF Applications in Radio and Television Receivers
• FM Tuners
• Low Noise AM Mixer-oscillators
• IF Amplifiers in AM/FM Receivers
BF494 Package

Package
BF494 Manufacturer
ON Semiconductor (Nasdaq: ON) is a disruptive technology firm that is helping to build a brighter future. It was founded in 1999. With an emphasis on automotive and industrial end-markets, the firm is speeding change in megatrends like as vehicle electrification and safety, sustainable energy grids, industrial automation, and 5G and cloud infrastructure. Through a highly specialized and unique product range, Onsemi provides intelligent power and sensor solutions that address the world's most pressing concerns and pave the path for a safer, cleaner, and smarter world.
For automotive, communications, computer, consumer, industrial, LED lighting, medical, military/aerospace, and power applications, products include power and signal management, logic, discrete, and bespoke devices. In North America, Europe, and Asia Pacific, ON Semiconductor has a network of production plants, sales offices, and design centers. In 2016, ON Semiconductor, based in Phoenix, Arizona, generated $3.907 billion in revenue, placing it among the top 20 semiconductor sales leaders in the world.
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Datasheet PDF
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