Monday, February 17, 2014

Introducing of LASCR Light Activated Silicone Controlled Rectifier

Robometricschool. - There are many kinds of active electronic component that made from semiconductor materials like silicone and germanium. One electronic component that very popular in electronic is Silicone Controlled Rectifier (SCR). One kinds of SCR is LASCR that stand for Light Activated SCR.

Figure 1. LASCR Symbols and Construction

In this time we want to share with you as introduction of LASCR Light Activated Silicone Controlled Rectifier as active electronic component.

According article that posted by circuitstoday blog describe that Light activated SCR (LASCR) or a Photo SCR  is just an ordinary SCR except that it can also be light triggered. Most LASCRs also have a gate terminal for being triggered by an elec­trical pulse just as a conventional SCR. 

The basic construction of an LASCR is shown in figure 1 above. The schematic symbols most commonly used for the LASCR are shown in figure.  Some LASCRs have clear windows in their cases so that light sources from other devices can be cou­pled to them. Many have the light source encapsu­lated in the same package so that a relay is formed. When the light falling on depletion layers is strong enough, valence electrons are dislodged from their orbits and become free electrons. When these free electrons flow out of the collector of one, transistor into the base of the other.

The positive feedback starts and the LASCR turns on just like a normal SCR, the LASCR will continue to conduct even if the light source is removed. For maximum sensitivity to light, the gate is left open, as shown in figure. 

Trigger adjust can be included if an adjustable trip point is desired as shown in figure. The gate resistor diverts some of the light produced electrons and alters the sensitivity of the circuit to the incoming light. The devices are for low power applications.

And to know more about LASCR application schematic we will show you the application of  LASCR component like in figure 2 below.

Figure 2. LASCR Application Schematic (


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