TSOP17XX is one of the most commonly used Infrared Receiver that is used in Pulse Code Modulation remote controlled systems such as TVs, DVD Players, and Burglar Alarms etc. The component consist of a PIN diode, preamplifier and an internal filter for PCM frequency, along with this an epoxy package is designed as an IR filter.
To amplify the coded pulse from the IR transmitter the TSOP17XX module has an inbuilt control circuit. When a PIN photodiode receives the signals, it send out a generated signal, which works as an input signal for the automatic gain control. The output is fed back to AGC, to adjust the gain to a suitable level so that it can obtain various range of Inputs. The undesired frequencies are filtered by passing the signals from the AGC through a band pass filter. Up next is the demodulator which receives the signal and this demodulated output drives an NPN transistor. The collector output of the transistor is obtained at pin 3 of TSOP module.
Different members of the TSOP17XX series are sensitive to different centre frequencies of the IR spectrum.