BF494 Transistor: Circuits, Pinout, and Datasheet

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.

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Footprint

3D Model

• 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

ON Semiconductor BF494 technical specifications, attributes, parameters and parts with similar specifications to ON Semiconductor BF494.

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.

• HF Applications in Radio and Television Receivers

• FM Tuners

• Low Noise AM Mixer-oscillators

• IF Amplifiers in AM/FM Receivers

Package

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