In this manual you can learn info such as sensor, amplifier, pyroelectric sensor, application circuit, and mounting. The manual gives the reader info around comparator, pyroelectric, circuit, motion detector circuit, and motion detector.
There are many info about detector circuit, infrared radiation, supply, gain, and radiation are explained inside this manual. Here are taken from the manual:
Figure 1 shows how typically, the FET source terminal pin 2 connects through a pulldown resistor of about 100 K to ground and feeds into a two stage amplifier having signal conditioning circuits. Each of the two cascaded stages has a gain of 100 for a total gain of about 10,000. The amplifier is typically bandwidth limited to below 10Hz to reject high frequency noise and is followed by a window comparator that responds to both the positive and negative transitions of the sensor output signal. A well filtered power source of from 3 to 15 volts should be connected to the FET drain terminal pin 1. The PIR325 sensor has two sensing elements connected in a voltage bucking configuration. This arrangement cancels signals caused by vibration, temperature changes and sunlight.
Additionally, this manual contains information regarding range, application, output, and infrared.