Optocoupler Turn On: Varying Emitter Voltage

Thread starter likephysics
Start date May 31, 2012

AI Thread Summary

An optocoupler activates when the emitter voltage is adjusted, with a specified input voltage of 5V and a 1V drop across the optocoupler. The total current flowing is 4mA, and the Vcc on the transistor side is set at 12V. To ensure the transistor turns on, the emitter voltage must be above a certain threshold. It is suggested that the transistor will activate when VCE exceeds 0.2V. Proper voltage management is crucial for reliable optocoupler operation.

May 31, 2012

likephysics

When exactly does a opto coupler turn on, if the emitter voltage is varied.
See attached.
Input voltage for the opto is 5V. Drop across the opto is 1v. Total current flowing is 4mA
The Vcc on transistor side is 12v.
What should the emitter voltage be, so that the transistor turns on.

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Jun 1, 2012

NascentOxygen

Staff Emeritus

Science Advisor

Homework Helper

I'd say it can turn on when V_CE>0.2V

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