onsemi BU806

Overview

BU806 from STMicroelectronics is a medium-voltage NPN Darlington transistor in TO-220 package, featuring integrated antiparallel collector-emitter damper diode, 400 V VCBO, 200 V VCEO, and 8 A continuous collector current. It is engineered for horizontal deflection stages in monochrome CRT video displays requiring fast switching and low base-drive requirements.

For engineers reviewing the BU806 datasheet, BU806 pinout, BU806 application, or BU806 equivalent, key selection criteria include sustaining voltage (VCEO(sus) = 200 V), saturation performance (VCE(sat) = 1.5 V @ IC = 5 A, IB = 50 mA), damper diode forward voltage (VF = 2 V @ IF = 4 A), and thermal resistance (Rthj-case = 2.08 °C/W).

Technical Context

The BU806 implements a silicon epitaxial planar Darlington configuration with an integrated base-emitter speed-up diode to reduce storage time (ts = 0.55 µs) and improve turn-off response. Its internal damper diode enables self-contained flyback energy handling in horizontal output circuits without external components.

Designed specifically for CRT horizontal deflection, it operates under pulsed conditions (300 µs pulse width, <1.5% duty cycle) and supports high-voltage switching up to 400 V collector-base with robust junction temperature tolerance (Tj max = 150 °C) and low leakage (ICES = 100 µA @ VCE = 400 V).

Key Specifications

Pinout & Package

Supplied in TO-220 plastic package with isolated mounting flange (pin 2 connected to collector). Standard 3-pin layout: Pin 1 = Base, Pin 2 = Collector (tab), Pin 3 = Emitter.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Darlington horizontal output applications.

Compared with BU807 and BU2508DX, the BU806 uniquely balances 200 V sustaining voltage, integrated damper functionality, and TO-220 compactness-making it optimal for cost-sensitive, space-constrained monochrome CRT horizontal stages where external diodes must be avoided.

Availability

BU806 is available at Aetrix Electronics and suitable for monochrome CRT horizontal deflection, legacy TV service replacement, and industrial CRT-based instrumentation requiring stable component supply and long-lifecycle support.

Supply support for BU806 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing analog, power, and discrete devices for industrial, automotive, and consumer applications.

The BU-series Darlington transistors target high-reliability analog video systems, specifically engineered for horizontal deflection in CRT displays with emphasis on integrated protection, thermal robustness, and timing precision.

FAQ

Is BU806 pin-compatible with BU807?

Yes, BU806 and BU807 share identical TO-220 package, pinout (Base–Collector–Emitter), and mechanical dimensions. However, BU807 has lower VCEO(sus) = 150 V and reduced VCBO = 330 V, making it unsuitable for designs requiring 200 V sustaining voltage or 400 V collector-base blocking.

Does BU806 require an external base speed-up capacitor?

No. The BU806 integrates a base-emitter speed-up diode, eliminating the need for external capacitors or resistors to reduce storage time. Measured storage time is 0.55 µs under standard test conditions (IC = 5 A, IB1 = 50 mA, IB2 = −500 mA), sufficient for 15.625 kHz horizontal scanning.

Can BU806 be used in modern LCD or LED display power supplies?

No. The BU806 is optimized for CRT horizontal deflection with specific timing (ton/toff/ts), high-voltage flyback handling, and integrated damper diode functionality. Modern switch-mode power supplies use different topologies, control schemes, and voltage/current profiles incompatible with this Darlington's design intent.

What is the maximum safe operating case temperature for BU806?

The BU806 is rated for total power dissipation of 60 W only when case temperature remains below 25 °C. With Rthj-case = 2.08 °C/W, junction temperature reaches 150 °C at 60 W and 25 °C case. For continuous operation, maintain Tcase ≤ 25 °C using adequate heatsinking; derate linearly above that point per thermal data.