Explain the construction and working of LASCR?

Answer 1

it is a light activated silicon controlled rectifier that uses light to trigger the scr instead of a signal at the gate. The window for the light activation is where the gate normally is and the ligth excites the electrons thus triggering the scr.

The Light Activated Silicon Control Rectifies start conduction when it is forward biased. For this purpose the cathode is kept at negative positional and anode is at positive positional. We apply a positive clock at the gate terminal and so the Silicon Control Rectifies turns ON.

When forward bias voltage is applied to the Light Activated Silicon Control Rectifies, or applied light of a required level the junction J1 and J3 become forward bias while the junction J2 become reverse bias. When we apply a clock pulse at the gate terminal, the junction J2 become forward bias and the Light Activated Silicon Control Rectifies start conduction.

The Light Activated Silicon Control Rectifies turn ON and OFF very quickly, At the OFF state the Light Activated Silicon Control Rectifies provide infinity resistance and in ON state, it offers very low resistance, which is in the range of 0.01Ω to 1Ω

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