Switching circuit diagram with photocoupler

Published:2011/5/13 4:16:00 Author:Ecco | Keyword: Switching circuit, photocoupler | From:SeekIC

According to the figure 1, when the input signal ui is in low level, the transistor V1 is placed in a closed state, the current of LED in photocoupler B1 is nearly 0, the resistance between Q11 and Q12 is so high to result in the switch be off ; When the ui is in high level, the LED of Bi is lit, the resistance between Q11 and Q12 becomes low，the switchis switch on . As Ui is in low level, switch is impassable, the circuitry is in high level conducting state. In the same argument, in the figure 2, because of having no semaphore(Ui for low level), switch turns on, the circuitry is in low level conducting state.



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