L200 Light Controller

This is a circuit of L200 light controller. The output of this circuit is controlled by the surrounding environment’s brightness.  If the brightness increases, the output voltage will increases as well. Here is the circuit :

The R1 and photoresistor are connected in parallel. They are used as regulator.  If we connect the the photoresistor in parallel with R2, we will obtain the opposite effect such as when the ambient light increases, the light will be dimmed. [Source: STMicroelectronics Application Note]