The picture shows the internal structure block diagram of the LED infrared receiving head, which integrates circuits such as automatic gain amplifier, band-pass filter, demodulator, etc., and some also include limiter circuits, comparators and integrators, so a small receiving head In fact, a lot of circuits are integrated inside.

Infrared receiver application principle diagram, because the receiver is easily interfered by external signals, especially infrared light, a filter capacitor is added to both ends of the power supply of the LED infrared receiver, that is to say, an electrolytic capacitor is connected between VCC and GND. Capacitors and ceramic capacitors can be designed according to the data provided by the manufacturer; at the same time, a resistor is pulled up on the output pin to make the signal more stable; a resistor in series with the VCC input, which forms an RC with the capacitor, and also acts as a current limiter The pressure-reducing effect further strengthens the stability of the receiving head.

SFH and RPM is a special infrared receiving circuit, which integrates the infrared receiving tube and the amplifying circuit. It is small in size (the size is equivalent to a mid-power triode), has good sealing, high sensitivity, and low price. It is sold in the market. The price is only a few yuan. It has only three pins, namely the positive pole of the power supply, the negative pole of the power supply and the signal output terminal. Its working voltage is about 5V. As long as it is connected to the power supply, it is a complete infrared receiving amplifier, which is very convenient to use.

Its main functions include amplification, frequency selection, and demodulation. The input signal must be a modulated signal. After receiving amplification and demodulation, the original signal will be output directly at the output terminal. So as to make the circuit to be the most simplified! Sensitivity and anti-interference are very good, so it can be said to be an ideal device for receiving infrared signals.

         The LED infrared receiving head is usually composed of an infrared receiving diode and an amplifying circuit. The amplifying circuit is usually composed of an integrated block and a number of resistors and capacitors, and needs to be packaged in a metal shielding box. Therefore, the circuit is more complicated and the volume is small. Not as big as a 7805!