PT8A975P

The PT8A975P is a complete infrared remote control receiver subsystem manufactured by Princeton Technology Corporation. This highly integrated device incorporates a PIN photodiode, preamplifier, automatic gain control (AGC) circuit, band-pass filter, demodulator, and output driver all in a single 8-pin DIP package. Designed to receive the modulated IR signals from standard remote control transmitters operating at 38kHz carrier frequency, it produces a clean digital output (active low) directly compatible with microcontroller I/O ports. The built-in AGC circuit automatically adjusts gain to handle varying signal strengths and ambient light conditions, while the integrated band-pass filter is tuned to the 38kHz carrier to reject out-of-band noise and interference. The wide supply voltage range of 2.7V to 5.5V makes it compatible with both 3.3V and 5V systems. Typical operating current is only 1.5mA, making it suitable for battery-powered applications. The device features high immunity to electromagnetic interference and ambient light disturbances, ensuring reliable operation in various environments. With no external components required, it simplifies PCB design and reduces overall system cost. The PT8A975P is widely used in televisions, set-top boxes, DVD players, air conditioners, audio equipment, and other consumer electronics requiring infrared remote control reception capability.

The PT8A975P operates by receiving modulated infrared light from a remote control transmitter and converting it into a digital electrical signal representing the transmitted data. The internal PIN photodiode converts incoming infrared light photons into electrical current. This tiny photocurrent is first amplified by a low-noise preamplifier stage. The Automatic Gain Control (AGC) circuit that follows dynamically adjusts the amplifier gain based on the average signal level. This is critical because IR signal strength varies greatly depending on distance, angle, and ambient light conditions — the AGC ensures both very weak signals (long range) and very strong signals (close proximity) are properly amplified without clipping. The amplified signal then passes through a band-pass filter that is tuned to the 38kHz carrier frequency. This filter attenuates signals outside the passband, effectively rejecting ambient light modulation (which is typically at much lower frequencies from fluorescent lights) and other electrical noise. After filtering, the signal goes to a demodulator circuit that extracts the envelope (the data modulation) from the 38kHz carrier. This demodulation stage typically uses a peak detector or comparator with appropriate hysteresis to produce a clean digital output. The output is an active-low signal — when a valid 38kHz carrier is detected, the output goes low; when no carrier is present, it returns high. This output directly matches the inverted data format used by most IR remote protocols (NEC, RC5, RC6, etc.). The entire signal chain is designed to provide high sensitivity while maintaining good noise immunity, and the chip includes various protection and filtering features to ensure reliable operation even in electrically noisy environments.

• TV and display remote control receivers
• Set-top box (STB) IR input
• DVD/Blu-ray/media player receivers
• Home air conditioner remote control
• Home theater audio systems
• Appliance remote control
• Industrial remote I/O systems
• Automotive rear-seat entertainment