BF258 Pinout, Equivalent, Application, Datasheet

The BF258 is an NPN high-voltage video amplifier transistor designed for wideband and fast signal amplification. This article explains the BF258 pinout, electrical ratings, working principle, applications, and suitable alternatives for high-voltage video and RF circuits.

Introduction

The BF258 is a high-performance NPN bipolar junction transistor intended for video amplification and wideband signal processing. With very high voltage capability and solid power dissipation, it is commonly used in CRT video stages, oscilloscopes, and other high-voltage analog amplifier designs.

Pin Configuration / Pinout of BF258 Transistor

Understanding the BF258 Pinout Configuration

The BF258 is housed in a rugged TO-39 metal package, which provides excellent heat dissipation and electrical shielding. The three terminals are:

Correct orientation of the BF258 pinout is critical when working with high-voltage circuits.

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

BF258 Key Features

• NPN high-voltage video amplifier transistor
• Designed for wideband and fast signal amplification
• Very high collector-emitter voltage capability
• Stable thermal performance in TO-39 metal can
• Suitable for video, pulse, and RF amplifier circuits
• Reliable operation in high-stress environments

BF258 Specifications/Characteristics

• Collector-Emitter Voltage (Vceo): 250V
• Collector-Base Voltage (Vcbo): 250V
• 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 BF258 Transistor

• High-voltage video amplifier circuits
• CRT display and monitor stages
• Oscilloscope vertical amplifier stages
• Wideband and pulse amplifier circuits
• High-voltage RF signal amplification

BF258 Equivalent / Alternatives

(Verify pin compatibility before using substitutions)

Equivalent Transistors: BF257, BF259
Alternative Devices: 2N3583, MJE340 (with proper biasing)

More Circuit Layouts

Working Principle of BF258

The BF258 operates by using a small base current to control a much larger collector current. When the base-emitter junction is forward biased, carriers flow efficiently through the transistor, enabling stable amplification of high-frequency video signals at high operating voltages.

Frequently Asked Questions (FAQ)

Q1: What makes BF258 suitable for video amplifiers?
Its high voltage rating and wide bandwidth make it ideal for video amplification.

Q2: What package is BF258 available in?
BF258 is available in a TO-39 metal package.

Q3: Can BF258 handle high-voltage signals safely?
Yes, it supports up to 250V collector-emitter voltage.

Q4: Is BF258 usable in RF circuits?
Yes, it can be used in medium-frequency RF and pulse circuits.

Conclusion

The BF258 NPN high-voltage video amplifier transistor is a robust solution for wideband and high-voltage applications. With strong thermal handling, fast response, and proven reliability, it remains a dependable choice for professional video and analog amplifier designs.

Datasheet of BF258 Transistor

Click the following Button below to download the datasheet of BF258 :

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