That circuit with NPN transistor(s) would buzz with every pulse. The question that needs to be answered by arunsharma0731 is whether he is using continuous 38KHz IR or pulsed 38KHz. Since he referred to a person passing and a security system, I assumed the range of his device is more than several cm. Thus, it is likely his IR signal is pulsed as is the signal from the detector. Hence a simple comparator or on/off photosensor will not work. Of course, if the output of his detector is not pulsed, then a simpler photodetector may work.