QT4503

Overview

The QT4503 is a single-channel optoisolator manufactured by QT Brightek, featuring a transistor output with an accessible base terminal. It provides high-voltage isolation of 5000Vrms between input and output circuits. The device operates within a temperature range of -55°C to 100°C and is housed in an 8-DIP package with a 0.300-inch width. Key electrical parameters include a maximum forward current of 25 mA, a typical forward voltage of 1.45 V, and a collector-emitter voltage rating of 20 V. The unit supports a DC input type and offers a current transfer ratio ranging from 19% to 50% at a test current of 16 mA.

Feature Summary

• Provides galvanic isolation for signal transmission between low-voltage control circuits and higher-voltage loads.
• Includes an integrated base terminal on the phototransistor output to allow for external biasing or speed adjustment.
• Designed for robust performance across wide industrial temperature ranges.

Applications

• Industrial automation control systems requiring isolated switching.
• Power supply feedback loops for voltage regulation.
• Microcontroller interface circuits for noise immunity.

Procurement Notes

Verify the specific datasheet version for the QT4503 to confirm pinout compatibility and absolute maximum ratings before integration. Ensure that the operating conditions remain within the specified thermal and electrical limits defined by the manufacturer. Cross-reference the component marking with official documentation to authenticate the source and avoid counterfeit parts during procurement.

Selection Notes

Select this component when a transistor output with base access is required for customizable drive characteristics. Consider the 5000Vrms isolation voltage for safety-critical applications. Evaluate the 8-DIP package constraints against available PCB real estate. Compare propagation delays if high-speed data transmission is necessary, as this device is optimized for general-purpose isolation rather than ultra-high-speed digital signaling.

Part Context

The QT4503 belongs to the Optocoupler series produced by QT Brightek. It shares the 8-DIP form factor common to many standard isolation devices but distinguishes itself through the inclusion of the base terminal feature. This places it in the category of transistor-output isolators designed for flexible circuit design where standard fixed-gain outputs may not suffice.

Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided documentation. Verify pin-to-pin compatibility with existing designs before considering alternative manufacturers.