@ photo-diode is a component in which a p-n junction exist.and the operation through photo diode in reverse bias and less sensitive .and photo detector or optical sensor may be...

ok

i agree system must be compact without using txr..but how stepping down of ac can be done without trasformer?

any type of sensor changes the physical quantities to proportional function of voltage,resistance,mechanical deformation,.

the idea of this type of ic is not reliable must use transformer.