Power Transistor BU120 NPN TO-3

Power Transistor BU120 NPN TO-3

Transistors

Reference: TRBU120

Part.No: BU120

€5.50

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The BU120 is a high-voltage NPN power transistor in a TO-3 metal package. A classic switching component for television deflection circuits, flyback transformers, and industrial SMPS applications requiring rapid high-voltage commutation and robust heatsinking.

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Description
Product Details

BU120 High-Voltage Switching Transistor – Industrial & TV Deflection Circuits

The BU120 is a robust NPN power transistor specifically engineered for high-voltage switching applications. Its TO-3 metal case allows direct bolting to large heatsinks, making it the preferred choice for television deflection stages, ignition coil drivers, and switching power supplies that demand reliable commutation at elevated voltages.

Functions & Applications

High-Voltage Switching: Optimized for rapid ON/OFF commutation of large voltages in flyback transformers and deflection circuits.
Robust TO-3 Package: Metal case designed for direct bolting to industrial heatsinks with maximum thermal contact.
Industrial Reliability: Proven component in television and SMPS applications where robust switching performance is critical.
Heatsink Ready: Includes threaded mounting hole; use insulating mica pad and thermal compound for safe operation.

Technical Specifications

Parameter	Value / Specification
Transistor Type	BJT (Bipolar Junction Transistor)
Polarity / Channel	NPN
Package / Case	TO-3
Package Type	TO-3 Metal Case
Mounting Type	Bolted Heatsink (Screw-Fastened)

Frequently Asked Questions

Q: Can the BU120 be used for audio amplification?
A: No. The BU120 is designed exclusively for fast switching (ON/OFF) in high-voltage applications. It is not optimized for linear amplification, and audio signals will suffer severe distortion.

Q: What insulation is needed between the transistor and heatsink?
A: Always use an insulating mica pad (typically 0.3–0.5 mm thickness) between the TO-3 case and the heatsink, along with thermal compound, to prevent electrical contact while maintaining good heat transfer.

Notes

The BU120 is a vintage/legacy industrial component. It is optimized for switching applications only and requires proper heatsinking with insulating mica pad for safe operation.

Note: Price refers to one (1) piece. The component is shipped in bulk without individual packaging.

Transistor Type: BJT (Bipolar Junction Transistor)
Transistor Polarity / Channel: NPN
Transistor Case Style: TO-3

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