Fairchild FOD2741A Data Handbook
Summary
This advanced integrated circuit combines an optocoupler, precision reference voltage source, and error amplifier into a single package, providing superior signal isolation. Designed for power supply designers crafting highly regulated AC to DC power supplies and DC/DC converters, this series offers enhanced stability and reduced component count. The manual details the electrical characteristics, functional diagrams, pinouts, and deep technical data required for implementing reliable, high-performance isolated systems.
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OPTICALLY ISOLATED ERROR AMPLIFIER
FOD2741A FOD2741B FOD2741C
DESCRIPTION The FOD2741 Optically Isolated Amplifier consists of the popular KA431 precision programmable shunt reference and an optocoupler. The optocoupler is a gallium arsenide (Ga As) light emitting diode optically coupled to a silicon phototransistor. It comes in 3 grades of reference voltage tolerance = 2%, 1%, and 0.5%. The Current Transfer Ratio (CTR) ranges from 100% to 200%. It also has an outstanding temperature coefficient of 50 ppm/°C. It is primarily intended for use as the error amplifier/ reference voltage/optocoupler function in isolated ac to dc power supplies and dc/dc con- verters. When using the FOD2741, power supply designers can reduce the component count and save space in tightly packaged designs. The tight tolerance reference eliminates the need for adjustments in many applications. The device comes in a 8-pin dip white package.
FEATURES
FUNCTIONAL BLOCK DIAGRAM
Optocoupler, precision reference and error amplifier in single package 2.5V reference CTR 100% to 200% 5,000V RMS isolation NC LED UL approved E90700, Volume 2 CSA approval 1296837
VDE approval 40002463 BSI approval 8702, 8703 Low temperature coefficient 50 ppm/°C max
FOD2741A: tolerance 0.5% FOD2741B: tolerance 1%
FOD2741C: tolerance 2% NC GND
APPLICATIONS Power supplies regulation DC to DC converters
PIN DEFINITIONS Pin Number Pin Name Pin function description
NC Not connected
Phototransistor Collector Phototransistor Emitter
NC Not connected GND Ground COMP Error Amplifier Compensation. This pin is the output of the error amplifier. * FB Voltage Feedback. This pin is the inverting input to the error amplifier LED Anode LED. This pin is the input to the light emitting diode.
* The compensation network must be attached between pins 6 and 7.
© 2003 Fairchild Semiconductor Corporation Page 1 of 15 12/9/04
Page Summary Contents For Fairchild FOD2741A Data Handbook
Manual Details
| Brand | Fairchild |
|---|---|
| Pages | 15 |
| File Size | 191.33 KB |
| Published | June 18, 2026 |
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Frequently Asked Questions
What is the primary use case for the FOD2741 Optically Isolated Amplifier?
It is primarily intended for use as an error amplifier/reference voltage/optocoupler function in isolated AC to DC power supplies and DC/DC converters.
Do I need external adjustments when using this device?
No. The tight tolerance reference eliminates the need for adjustments in many applications.
What is the maximum achievable isolation level?
The device provides 5,000V RMS isolation.
Which variant should I use if I require the lowest voltage tolerance?
Use the FOD2741A variant, which has a tolerance of 0.5%.