LM4766 is a two-channel high-power amplification integrated circuit introduced by NS, and each channel can output 40W average power on the 8Ω load, and the distortion is less than 0.1%, in the product line of the National Semiconductor Company, LM4766 is classified. "Overture" series, which belongs to the highest-end single-channel audio power amplification integrated block. LM4766 indicators are very attractive, good signal to noise and distortion power integrated circuits that are very good, LM4766 can do in the human ear can hear the band, with only 0.06% in the case of distortion and 30W power output Noise value, the design capacity of the power integrated block of the national semiconductor can be seen. We have reason to believe that if with good circuit design, LM4766 can play the effect may not only whether "reach HI-FI" will be able to comment. Of course, that does not mean that whenever using the LM4766 power blocks, we will be able to achieve HI-FI effect! The design of the amplifier is a systematic project, and the horse tiger will take some good performance naturally. The internal manifold also has a comprehensive protection measures: (output automatically turned off when 165 ℃, automatically return to work when 155 ℃) overvoltage, undervoltage, overload, over-temperature, and the company's patent - SPIKE peak protection safe operating area (guarantee integrated amplifier final stage of the safe operating area curve for the pipe work etc.). It can be said that the power amplifier designed with the LM4766 is generally possible to achieve considerable security. In addition, both channels inside the LM4766 have a separate mute circuit and is co-extracted through two pins. Its role is to close the input of LM4766, so that no signal inside the amplifier output, after which two pin connector in a manner, to eliminate the impact of the boot process. From DataSheet we can see that the power supply voltage of the LM4766 reaches + -30V, and there is enough signal excitation, then the LM4766 pushes the power of the output 40W, this power, which has been capable of moving most of the multimedia speakers push instill obedience. What's more, I usually listen to music when probably will 1,2W power is sufficient rang. Based on past experience, LM4766 power although not great, but the thrust was strong, sound thick, rich, soft Naiting grace, using it to promote small and medium sized speakers, can effectively avoid the small speakers sound thin, delicate and so prone to deficiencies, even enjoy the sound tube-like machine.
The figure is the LM4766 application of electrical schematics:
(B) production guidance
FIG press finished printed circuit board, the assembly can be welded. Welding the first part can be plugged prior to welding, since the welding from the smallest parts, replacement adhesion electrolytic capacitor as the circuit board to be noted that the polarity of the surface, otherwise it will be a breakdown, the metal membrane capacitance there is no polarity, but preferably in the same direction, so more neat appearance. Due to the poor performance of electrolytic capacitors at high frequencies, so the addition of polypropylene capacitors 104 to improve the sound quality, can not find a place close available, the higher the pressure the better, which is aligned with the principles of the electrolytic capacitor by medium and small parallel 4700UF .
Two inductors No. 18 enameled wire wound available 10 turns on the resistor 10Ω2W, both end surfaces of the paint scraped off, the two solder feet across the resistor. Since No. 18 enameled wire wound thicker bad, enameled wire can be left for a long period, from the middle portion of each of the resistor 5 turns around the sides, so that more effort, it is also about the more beautiful. This figure inductance value 0.47mH, but most not generally commercially available low inductance DC resistance required (can be roughly determined from the body), whereas the present embodiment requires a low inductance DC resistance, inductance value of the accuracy is still followed, so we use self thicker enameled wire wound inductors to. Since the DC resistance of the inductor is too large, the signal blocking way, it is rather not inductance means (short-circuit resistance directly), nor those who buy the chip inductor.
(C) the installation and commissioning
The circuit size of the fins, to follow their own style preferences later, the best buy 10CM X 11CM X 3MM radiator plate. LM4766 between the fins and to apply a thermal paste, to help conduct heat.
After all installed, you can test it, turn the volume to the maximum, use the multimeter DC voltage file to detect the output, the voltage should be between 0-0.2V. The output of the ideal value of zero (because the symmetrical positive and negative power is applied), but there must be an error part, the output voltage slightly. Then put multimeter to the lowest AC voltage file and extract touch input (touch IN enough, does not have to be met), to give some body induction noise, then multimeter indicators should be swinging, if measured voltage is too large, it may not be 47KΩ resistor connected between the input terminal and the ground, it should be the case after connecting through improved.
4 4700UF large capacity filter capacitor, with high-grade toroidal transformer with a power of 150W, the output voltage is 18V + 18V.
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