My Inquiry
My Account
Motorola BU508A
- Part No.:
- BU508A
- Manufacturer:
- Motorola
- Category:
- Single Bipolar Transistors
- Package:
- TO-247-3
- Datasheet:
-
BU508A.pdf
- Description:
- TRANS NPN 700V 8A TO-247-3
- Quantity:
- Payment:
- Shipping:
Inventory:2,102
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
BU508A from STMicroelectronics is a high-voltage, fast-switching NPN power transistor in an ISOWATT218 (TO-218) insulated package, rated for VCES = 1500 V, IC = 8 A, and Ptot = 125 W at Tc = 25 °C. It features hollow emitter structure for enhanced switching speed and is designed for horizontal deflection circuits in color TV systems.
For engineers reviewing the BU508A datasheet, BU508A pinout, BU508A application, or BU508A equivalent, key selection criteria include its 1500 V collector-emitter blocking voltage, 7 µs storage time under inductive load, 1 V VCE(sat) at 4.5 A, insulation withstand of 2500 VRMS, and thermal resistance of 1 °C/W junction-to-case.
Technical Context
The BU508A employs Multiepitaxial Mesa technology and a hollow emitter design to achieve fast switching with low saturation voltage. Its safe operating area supports high-voltage inductive switching at up to 700 V sustained VCEO and 15 A peak current (tp < 5 ms).
It operates with DC current gain (hFE) specified at test conditions, exhibits fT = 7 MHz at IC = 0.1 A, and maintains stable performance across Tj = –65 to 150 °C with Rthj-case = 1 °C/W in TO-218 package.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCES | 1500 V - Enables direct use in high-voltage horizontal deflection flyback stages without external snubbers. |
| IC | 8 A continuous - Supports sustained horizontal scan current drive in CRT TV output stages. |
| Ptot | 125 W at Tc = 25 °C - Requires heatsink mounting but avoids forced-air cooling in standard TV chassis. |
| ts | 7 µs - Limits energy loss during turn-off in inductive flyback operation at 15.734 kHz line frequency. |
| VCE(sat) | 1 V at IC = 4.5 A, IB = 2 A - Reduces conduction loss and thermal stress in high-duty-cycle switching. |
| Visol | 2500 VRMS - Allows direct mounting to grounded heatsinks without insulating washers per UL compliance. |
| fT | 7 MHz - Sufficient bandwidth for precise base drive control in analog horizontal timing applications. |
Pinout & Package
BU508A is housed in an ISOWATT218 (TO-218) fully insulated package with three leads: Collector (pin 1), Base (pin 2), Emitter (pin 3). The metal tab is electrically isolated from all terminals and rated for 2500 VRMS insulation to heatsink.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (Tab side, left) | Collector | Main high-voltage power terminal; connected to flyback transformer primary and HV supply rail. |
| 2 (Center) | Base | Current-controlled input; requires ~2 A peak drive for full saturation in line-output switching. |
| 3 (Right) | Emitter | Power return path; tied to ground or damper circuit in horizontal deflection output stage. |
Key Features
| Feature | Design Value |
|---|---|
| Hollow emitter structure | Reduces minority carrier storage, enabling 7 µs storage time for reliable 15.7 kHz line retrace. |
| Fully insulated package (UL compliant) | Eliminates need for mica washers or silicone pads when mounted to grounded metal chassis. |
| Multiepitaxial Mesa process | Delivers consistent VCEO(sus) ≥ 700 V and low leakage (ICES ≤ 2 mA at 1500 V, 125 °C). |
| Low Rthj-case | 1 °C/W enables 125 W dissipation with modest heatsink surface area in confined TV enclosures. |
Applications
| Color TV Horizontal Deflection | Monitor Flyback Power Switch |
|---|---|
Use Scenario: Driving flyback transformer primary in 15.734 kHz horizontal scanning circuits of analog CRT TVs. IC Role / Device Role / Timing Role: High-voltage NPN switch controlling energy storage and release in line-output stage. Use Value: 1500 V VCES withstands flyback voltage spikes; 7 µs ts ensures clean retrace without secondary breakdown. | Use Scenario: Regulating high-voltage B+ supply and generating EHT in CRT computer monitors. IC Role / Device Role / Timing Role: Primary-side power switch in self-oscillating or externally synchronized flyback converter. Use Value: 2500 VRMS insulation allows direct heatsink grounding, simplifying mechanical layout and reducing EMI coupling. |
| Industrial HV Pulse Generator | Legacy Broadcast Transmitter Stage |
Use Scenario: Generating controlled high-voltage pulses for plasma ignition or capacitor discharge systems. IC Role / Device Role / Timing Role: Fast-turnoff switch discharging HV capacitors into inductive loads. Use Value: 15 A ICM peak rating supports short-duration pulse currents; 1 V VCE(sat) minimizes pulse energy loss. | Use Scenario: Final amplifier stage in analog broadcast transmitters requiring rugged HV switching. IC Role / Device Role / Timing Role: Class-B or Class-C RF power switch operating below 1 MHz. Use Value: Stable hFE and fT = 7 MHz support linear gain control; 175 °C max Tj tolerance accommodates high ambient environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-voltage NPN switching applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| BU208A (TO-3) | Same VCES = 1500 V, higher Ptot = 150 W, Rthj-case = 1 °C/W, but non-insulated TO-3 package. | Requires insulating hardware for heatsink mounting; used where mechanical robustness outweighs isolation needs. | Select BU208A only if chassis grounding permits non-isolated mounting and higher power derating is required. |
| BU508AFI (ISOWATT218) | Identical package and insulation, but lower Ptot = 50 W and Tj(max) = 150 °C vs. BU508A's 125 W / 150 °C. | Targeted for lower-power deflection or standby-mode applications; not suitable for full-line-output duty. | Choose BU508AFI only for thermally constrained designs where peak dissipation remains below 50 W. |
Compared with BU208A and BU508AFI, the BU508A uniquely balances 125 W power handling, full 2500 V insulation, and 1500 V blocking in a single TO-218 footprint-making it the optimal choice for production-grade CRT horizontal output stages requiring safety-certified mounting and thermal headroom.
Availability
BU508A is available at Aetrix Electronics and suitable for color TV repair, CRT monitor refurbishment, and industrial HV pulse generator builds requiring stable component supply and long-lifecycle availability.
Supply support for BU508A 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, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.
The BU508A belongs to ST's legacy high-voltage power transistor family, engineered specifically for reliability-critical horizontal deflection and flyback power conversion in analog display systems.
FAQ
Is BU508A still in active production?
No-BU508A is marked as obsolete by STMicroelectronics per official documentation. However, Aetrix Electronics maintains verified legacy stock with full traceability, conforming to original specifications and packaging. Units are sourced from authorized channel inventory with full lot traceability and electrical validation.
Can BU508A replace BU208A directly on a PCB?
No-though both share identical pinout (C-B-E), BU508A uses ISOWATT218 while BU208A uses TO-3. Mounting hole pattern, tab isolation, and thermal pad geometry differ. Mechanical redesign and insulation verification are required before substitution.
What is the maximum safe operating voltage for BU508A in continuous DC mode?
The absolute maximum VCEO is 700 V with IB = 0, and VCES is 1500 V with VBE = 0. For reliable long-term operation, ST recommends limiting VCE to ≤ 80 % of VCEO (i.e., ≤ 560 V) under DC bias, especially at elevated junction temperatures.
Does BU508A require a base resistor when driven by a TTL-compatible signal?
Yes-TTL logic cannot source the 2 A peak base current needed for full saturation. A driver stage (e.g., Darlington or MOSFET-based) with appropriate base resistor (calculated for VBE(sat) ≈ 1.3 V and desired IB) is mandatory to ensure low VCE(sat) and avoid second breakdown during switching.
BU508A Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Motorola
- Series:
- -
- Package/Case:
- TO-247-3
- Packaging:
- Tube
- Product Status:
- Obsolete
- Transistor Type:
- NPN
- Current - Collector (Ic) (Max):
- 8 A
- Voltage - Collector Emitter Breakdown (Max):
- 700 V
- Vce Saturation (Max) @ Ib, Ic:
- 1V @ 2A, 4.5A
- Current - Collector Cutoff (Max):
- 1mA
- DC Current Gain (hFE) (Min) @ Ic, Vce:
- -
- Power - Max:
- 125 W
- Frequency - Transition:
- 7MHz
- Operating Temperature:
- 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-247-3
BU508A FAQ
1.How can I place an order for BU508A through Aetrix?
Please submit a Request for Quotation (RFQ) for BU508A on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for BU508A reliable?
The price and inventory of BU508A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BU508A is usually 5 days.
3.What payment methods are accepted for BU508A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BU508A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BU508A?
BU508A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BU508A order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for BU508A?
For technical support, including BU508A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BU508A requirements.
6.How does Aetrix verify that BU508A is sourced from the original manufacturer or authorized distributors?
All BU508A products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that BU508A meets industry standards.
7.What is the process for return or replacement of BU508A?
All BU508A units undergo pre-shipment inspection (PSI). If there is an issue with BU508A, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The BU508A part is unused and in its original packaging.
Return procedure for BU508A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
BU508A Tags
-
MMBT3906LT1G
onsemi
-
MMBT3904-7-F
Diodes Incorporated
-
MMBT3904LT1G
onsemi
-
MMBT3906-7-F
Diodes Incorporated
-
MMBT3904-TP
Micro Commercial Co
-
MMBT2222A-7-F
Diodes Incorporated
-
BC846BLT1G
onsemi
-
BC847B,215
Nexperia USA Inc.
-
SMMBT3904LT1G
onsemi
-
MMBT2222A-TP
Micro Commercial Co
-
MMBTA06LT1G
onsemi
-
MMBT2222ALT1G
onsemi
Tech Hub
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
LDO regulator guide covering low dropout voltage, power dissipation, thermal design, PSRR, output noise, capacitor stability, adjustable LDO circuits, LDO vs buck converter and datasheet selection chec…
Conditional Access Module guide covering CAM meaning, CI/CI+ interface, smart card authorization, DVB security workflow, TV and set-top box compatibility, internal electronics, ESD protection, connecto…
Guide to electronic component obsolescence covering EOL risk, PCN/PDN notices, last-time buy planning, replacement options, form-fit-function validation, counterfeit risk and BOM lifecycle management.
18650 battery guide covering lithium-ion cell basics, 3.6V/3.7V voltage, 4.2V charging, mAh and Wh capacity, protected cells, chargers, BMS, series-parallel packs, holders, welding and sourcing checks.…
Hall effect sensor guide covering working principle, linear and digital sensors, Arduino circuits, current sensing, speed detection, automotive applications, A3144 examples, signal filtering and datash…
Product Change Notification guide for electronic components, covering PCN meaning, PCN vs PDN/EOL, common change types, risk levels, form-fit-function review, engineering validation, BOM control, LTB/L…
A practical guide to blend door actuators, covering HVAC function, symptoms, location, AC and heater issues, reset and calibration, replacement cost, electrical diagnosis, compatibility checks, and rep…
