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[FAQ] What is Current Transfer Ratio (CTR)?

Aaditya V.
Mastermind 22636 points

FAQ: Isolation >> Opto-Emulators >> Current FAQ

What is Current Transfer Ratio (CTR)?

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    TI__Mastermind 22636 points

    What is Current Transfer Ratio (CTR)?

    Current Transfer Ratio (CTR) is a ratio of the output collector current to the input forward current and is represented in a percentage.

    CTR is a characteristic of analog opto-emulator or optocoupler devices. An example TI device for analog opto-emulator, please see the ISOM8110 family data sheet, and product information.

     

    The input forward current (IF) is the current going into the diode while the output collector current (IC) is the current flowing into the output transistor.

    • For CTR > 100%, the IC will be greater than the IF.
    • For CTR < 100%, the IC will be less than the IF.

    How is it represented in datasheets?

    How is CTR measured from a device?

    The diagram below shows the test circuit which is designed to measure the CTR for an analog opto-emulator.

    By applying the input forward current and applying a voltage to the collector-emitter, the output collector current can be measured.


    To find a SiO2 based TI opto-emulator, please see our Opto-emulators overview page at www.ti.com/opto-emulators