BF257 Pinout, Equivalent, Application, Datasheet

The BF257 is an NPN high-voltage video amplifier transistor designed for wideband and fast signal amplification. This article explains the BF257 pinout, electrical specifications, working principle, applications, and suitable equivalents to help you use it confidently in high-voltage and video amplifier circuits.

Introduction

The BF257 is a high-voltage NPN bipolar junction transistor optimized for video amplification and wideband signal processing. With high voltage handling, fast switching capability, and robust power dissipation, it is commonly used in CRT video stages, oscilloscopes, and high-speed amplifier circuits.

Pin Configuration / Pinout of BF257 Transistor

Understanding the BF257 Pinout Configuration

The BF257 is packaged in a TO-39 metal can, providing excellent thermal performance and shielding. It has three terminals:

Correct identification of the BF257 pinout is essential for safe operation in high-voltage and high-frequency applications.

Note: DATASHEET DOWNLOAD button is provided end of this article.

BF257 Key Features

• NPN high-voltage video amplifier transistor
• Designed for wideband and fast signal amplification
• Capable of handling high collector-emitter voltages
• Good thermal stability with metal TO-39 package
• Suitable for video, RF, and pulse applications
• Reliable operation in demanding environments

BF257 Specifications/Characteristics

• Collector-Emitter Voltage (Vceo): 160V
• Collector-Base Voltage (Vcbo): 160V
• Emitter-Base Voltage (Vebo): 5V
• Collector Current (Ic): 100mA
• Total Power Dissipation (Ptot): 5W
• Junction Temperature (Tj): 200°C
• Storage Temperature (Tstg): −65°C to 200°C
• DC Current Gain (hFE): 25
• Transition Frequency (fT): 90MHz

Key Applications of BF257 Transistor

• Video amplifier stages
• CRT display circuits
• Oscilloscope vertical amplifiers
• High-voltage signal amplifiers
• Pulse and waveform shaping circuits
• RF and wideband amplifier designs

BF257 Equivalent / Alternatives

(Verify pin compatibility before using substitutions)

Equivalent Transistors: BF258, BF259
Alternative Devices: 2N3583, MJE340 (with appropriate biasing)

More Circuit Layouts

Working Principle of BF257

The BF257 operates by allowing a small base current to control a much larger collector current. When forward bias is applied to the base-emitter junction, charge carriers flow efficiently through the transistor, enabling high-speed amplification of video and wideband signals even at elevated voltages.

Frequently Asked Questions (FAQ)

Q1: Is BF257 suitable for video signal amplification?
Yes, BF257 is specifically designed for video and wideband amplification.

Q2: What package is BF257 available in?
BF257 comes in a TO-39 metal package.

Q3: Can BF257 handle high voltages?
Yes, it supports collector-emitter voltages up to 160V.

Q4: Is BF257 good for RF applications?
Yes, it can be used in medium-frequency RF and pulse circuits.

Conclusion

The BF257 NPN high-voltage video amplifier transistor is a reliable choice for wideband, fast, and high-voltage amplification. With strong thermal performance, stable operation, and proven use in video electronics, it remains a valuable component in professional and legacy circuit designs.

Datasheet of BF257 Transistor

Click the following Button below to download the datasheet of BF257 :

More projects, You may like:

• Video Transmitter DIY Homemade FM Radio Transmitter
• Adjustable Power Supply DIY Battery Charger
• 12V-220V 500 Watt inverter DIY Homemade
• MPPT Solar Charge Controller DIY Homemade
• DIY LA4440 bass amplifier homemade

For more project and circuit diagrams, you can go through the Schematics in the main menu where you can find many interesting projects and circuit diagrams like audio amplifier circuits, voltage booster circuit, battery charger circuit and timer circuits etc., which are all beginner circuit projects. Feel free to check them out!

Thank you for visiting the article.