LM1875 Power amplifier production ----- lm1875 power amplifier

LM1875 Power amplifier production, LM1875 Power Amplifier Keywords: lm1875, amplifier, power amplifier, HIFI LM1785 is a high-fidelity film amplifier IC produced by NSC. It has strong adaptability, can be made into different forms of power amplifiers according to different approaches of OTL, OCL and BTL. This article modified an amplifier according to the OCL circuit recommended by the NSC manual. Review, I feel wide, and the sound is fascinating. In order to further play the potential function of the LM1875, the power amplifier is more sound, and it is repeatedly tried in the production process, and two experiences are obtained: 1. It is important for the choice of external components. Because the power amplifier circuit is simple, the peripheral components are small, so the relatively high-grade components, even high-quality components. Although the price is more expensive, the total cost will not be too high, and the sound is greatly improved. Second, in terms of the design and production of circuits, some small improvements can also achieve very ideal effects. The maximum loss of LM1875 is up to 30W, and the maximum output current 4A is up to 4A. Therefore, strive for the left and right channels of the power supply to be independent. Each channel power transformer power is about 100 VA, try to use excellent quality, rectifying bridge current> 5A, and electrolytic capacitors should be used in imported excellent quality or domestic genuine. Filter capacitors are preferably used in 1000μF x 2. Power power supply is directly taken from the filter capacitor terminal, do not pick up to the rectifier bridge to avoid communication. When designing a printed circuit board, you should follow the principle of signaling, power, and use a star ground. In fact, only five of the LM1875 is only 5 leads, and it is also very convenient to use the wiring bracket installation. However, it should be noted that the longer wire connection, especially the signal input line. Capacitors C2, C3, C4, C9 and input coupling capacitor C1 have a large impact on the sound quality of the whole machine, such as the use of French SOLEN products, the effect is very good. The resistance is selected for 1 / 2W metal film resistance. The volume potentiometer uses a Japanese Alps audio dedicated dual connect potentiometer, which mechanically has a small noise, and is well consistent. The original LM1875 amplifier uses an AC negative feedback circuit. A larger feedback capacitor has a larger impact on the whole machine, and the capacitor can be canceled. Since the LM1875's offset voltage is low, the maximum ± 2μV, after the feedback capacitor is canceled, the DC voltage of the measured output terminal is only 10mV, and the circuit is very stable. After the improved circuit is shown in Figure 5-21, a gain of 25 dB is assembled with high quality components. The Sony CDP-211 laser recorder with a homogers, pushes a pair of 4-inch bass, 1 inch treble small imported speaker, the tone is very delicate, full, and the positioning is clear and accurate. Especially when listening to strings and vocals, it is sweet and true. Figure 1: