TDA7331D

RF Demodulators is an important branch in communication and electronics．Currently, they are widely used in different industries, from the application of mobile phone to other professional fields．Among all kinds of demodulators, TDA7331D is one of the most popular ones, and it has many fields of application．

The main application of TDA7331D is signal receiving, especially for low-voltage signal．It is highly efficient in power consumption, small size, low coefficient of paralleling and cheap price．The maximum voltage it can bear is 15V．In addition, its bandwidth is wide, between 4.5-870MHz, which makes it capable of receiving signals in many frequency ranges．

Besides, this demodulator has the characteristics of strong anti-interference, wide dynamic range and low noise．There are no core components included in the demodulated board, so it is very easy to install．Thus, the board is widely applied in car alarms, linear radio and other wireless equipment．Moreover, it is also suitable in various places and longdistance remote control system．

To understand the working principle of TDA7331D, we need to explain FM demodulator first． It is a device to convert continuous frequency signal into signal without frequency variation．And the demodulator based on this principle consists of envelope detection and de-emphasis circuit．The detected signal is output as one with fixed amplitude after the demodulator．

As for TDA7331D, it mainly contains resonator, mixer, AGC and de-emphasis circuit．The mixer is used to mix original signal with a harmonic signal so that the original signal is lowered to its desired intermediate frequency．And the resonator is used as an oscillator．The AGC circuit will make the level of input signal adjust itself．The de-emphasis is used to eliminate distortion so that the sound output will be more clear．After these procedures, the signal output is complete．

In conclusion, TDA7331D is a kind of RF demodulator with wide application and great performance．It has strong interference-resistant feature, wide dynamical range and low noise．It is suitable for car alarm, radio and long-distance remote control．And it also consists of several components such as resonator, mixer and de-emphasis circuit．