5-10. Characteristics of Photocouplers (Current Transfer Ratio: CTR)

Current transfer ratio of transistor coupler: It is expressed by the amplification ratio of the output current with respect to the input current like the transistor hFE.

Current Transfer Ratio=CTR

 =IC/IF  =Output (collector) current/input current ×100 (%)

Characteristics of Photocouplers(Current Transfer Ratio: CTR)

E.g.)

When I= 5 mA is input, I= 10 mA is obtained.

CTR = I/IF = 10 mA/5 mA×100 (%) = 200%

Current Transfer Ratio

Reference: hFE of bipolar transistor

hFE  (DC current gain)

    = Collector current (IC)/base current (IB)

Reference: hFE of bipolar transistor

Chapter V : Optical Semiconductors (Isolators/Solid State Relays)

5-1. Types of Optical Semiconductors
5-2. Light-Emitting Principal of LEDs
5-3. The wavelength range of LEDs
5-4. What Is a Photocoupler?
5-5. Why Are Photocouplers Necessary?
5-6. Types of Photocouplers
5-7. Types of Photocouplers (Packages)
5-8. Types of Photocouplers (Internal Structure)
5-9. Safety Standards of Photocouplers
5-11. Principal Characteristics of Photocouplers (Trigger LED Current)
5-12. Aging Variation Data of Photocouplers
5-13. How to Use a Photocoupler
5-14. How to Use a Photocoupler “Input Current”
5-15. How to Use a Photocoupler “Output Current”
5-16. How to Use a Photocoupler “Output-Side Resistor”
5-17. How to Use a Photocoupler Check

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