Audio power amplifier made by la4445 integrated circuit, la4445 Power Amplifier
Keywords: la4445, power amplifier circuit diagram
Author: Wang Jianbo
The audio power amplifier is an important part of the sound system. The audio signal obtains sufficient push power feed to the speaker to complete the sound signal after the audio signal is enlarged. This stereo power amplifier is composed of the integrated circuit LA4445 designed by Sanyo Company. LA4445 is a two-channel OTL audio power amplification integrated circuit, and its typical output power is 2 × 5.5W. The internal protection circuit is prevented from turning the impact noise and a perfect internal protection circuit, which has the advantages of small harmonic distortion, less peripheral components, and high channel separation. It is widely used in the portable stereo, MP3 (MP4) player output power continues, computer multimedia Xague, etc. In order to improve the sound quality circuit, the tone adjustment circuit is used to control the input audio signal, and the bass is controlled and volume processing. The power amplifier is actually listening, the treble is soft and delicate, and the bass is full of round. Therefore, this is a power amplifier circuit that is very suitable for audio enthusiast beginners.
First, the working principle The circuit of the power amplifier consists of three parts, that is, the power supply circuit, the left and right channel power amplifier and tone adjustment circuit. The schematic diagram of the circuit is shown below. In order to adapt to different supply modes, the power interface uses a bridge rectifier circuit consisting of full bridge Bridge. It is almost a "universal" power interface. When using an external transformer to provide low voltage AC power, it is a rectifier circuit; When an external DC power supply is powered, it is a polar protection circuit that prevents damage to the circuit when the power supply is entered. The C1 constitutes a filter circuit, D1, and R1 constitute a power source indication, the actual operating voltage range of the circuit may be 10 to 15V. The power circuit diagram is shown in the figure.
The audio signal passes the J1 input, R1 is an impedance matching resistor such that the circuit can match the computer sound card, the MP3 (MP4) player headphone interface, and the like, and the resistor should be changed to 1KΩ audio signal when connected to the audio device with the line output. Immediately enter the attenuated tone control circuit for tone adjustment, the left and right two-channel component parameters are identical. In the left channels, C1, C2, R2, W1, etc. constitute a treble adjustment circuit; R3, R4, R5, C3, C4, W2, and the like constitute a bass adjustment circuit. The audio signal is coupled to the volume potentiometer W3 for the volume potentiometer W3, and C6 is to prevent self-excitement and reducing high frequency noise.
After the volume adjustment, the audio signal enters the input of the integrated circuit LA4445, and its 2 (5) pin is the same phase input terminal, 1 (6) pin is the inverting input terminal, C1, C5 is left, right two inputs, respectively. The coupling capacitor, C10, C11, and C6 are power supply decoupling capacitors, and the audio signal is coupled from C3 and C8 after amplification of the 0TL power. C7, C2 is a self-lifting capacitor, which can improve the output power. C4, R1 and C9, R4 constitute a speaker that prevents the self-binding network, J3, J4 is the output, and the load is 4Q, and the single effective power can reach 5.5W. The picture below shows the assembly effect.
Second, welding and installation
The PCB printed circuit diagram of the amplifier is shown in the figure above, as shown in the figure below. Component installation should follow the first small and old, first low, exterior, first easy, and finally the integrated circuit. The installation and welding should be made as follows:
1 Using the multimeter and other tools to check the quantity and quality of the component, and replace the unqualified components in time: 2 is installed by the hole distance determination element, the resistor is installed with horizontal installation, polyester accumulator, and the electrolytic capacitor uses vertical installation, and It is required to close the board. 3 Pay attention to whether the polarity of the electrolytic capacitor, diode is equipped with the correctness of the polarity. 4 Turn the integrated circuit screw to be carefully inserted into the circuit board in the heat sink, and the standby pin is inserted and soldered. Each solder joint heating time and use tin amount should be appropriate, prevent duel, fake welding, and short circuit, and then remove excess pins.
Third, audition and testing
After all components and insert welding, after careful examination, the rear can be tested. Use an external power adapter or transformer to introduce 10 to 15V AC stream power supply from J1, and measure the + VCC power supply with a multimeter DC voltage file. LED D1 illuminates, rotates the volume potentiometer counterclockwise to the head and connects the external speaker, then inputs the audio signal from 1, 2 and slowly rotates the volume potentiometer, should hear the pleasant signal in the speaker, indicating that the circuit is normal, if not The output signal indicates that the power discharge circuit does not work, and it is necessary to further check whether the integrated circuit and the peripheral component are installed normally.
Audio power amplifier element table
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