Hi-Fi Integrated Circuit (IC)Power Amplifier Application

Common market Hi-Fi integrated circuit (IC) power amplifier, mainly the following three products:

  1. National Semiconductor Corporation (NSC), on behalf of products LM1875, LM1876, LM3876, LM3886, LM4766 and so on. 

  2. Dutch Philips (PHILIPS), on behalf of products TDA15×× series, the more well-known is the TDA1514 and TDA1521. 

  3. Italian - French Microelectronics (SGS), the more famous is TDA20×× series and DMOS tube TDA7294, TDA7295, TDA7296. NSC warm neutral tones the company's products, Philips is more bright and delicate products.

Integrated Circuit (IC) power amplifier heat sink comes with two types of insulated and non insulated. Insulation class, such as the LM series suffix TF varieties, the overall molding process, simply fixed directly to manifold and radiator. Most of the exposed metal heat sink integrated amplifier is a non-insulated type, the heat sink generally negative supply connected, not to use its contacts with other parts of the amplifier (especially the case with the ground), otherwise the damage immediately Manifold. 

I found that by comparison, non-insulated block of the thermal resistance of the lower class of power amplifier output power to be slightly larger.

On the circuit in the form of choice, I think that, with the manufacturer to the voltage feedback circuit, and were also given on the basis of indicators to test out, since the recommendation, the circuit should be able to play better the performance of integrated block, the actual is also true. Current feedback and DC servo amplifier is an integrated application of a useful attempt, but the results should not be overstated.

DC voltage should not get too high, or only Manifold serious fever, and the sound quality deterioration, and may lead to over-voltage protection circuit malfunction. Should give priority to the use of manufacturers recommended voltage, if not, can be the limit × 85% voltage DC voltage, then divided by the DC voltage AC voltage was 1.25.

Amplifier without the use of power supply, but the power of the power capacity must be adequate. Desirable power transformer twice the total output power, and well shielded. Rectifier to choose low internal resistance, and both ends of each tube and on a small capacitor. Filter capacitance Enough is enough, do not blindly seek large, can be calculated per 10W 2200μF. If funded, with the transformer more effective.

Integrated amplifier with external components small, quality product should be selected. Coupling capacitor MKP better not to use electrolysis, the larger-capacity tantalum electrolytic bypass capacitors can be used, use a small capacitor CBB or MKP. To make use of rings of metal film resistors or Holco resistor, and power can not be less than 1/4W, 1/2W the conditional use. In the installed components should be checked before and pay attention to the error and the pair of. Do not blindly imported supplements, supplements, low cost components Moreover, many fakes.

Amplifier circuit layout should follow three principles:

  1. Point grounding. Integrated circuit, the input, the output filter capacitor to have a separate receipt to the "point", do not any overlap, to avoid the introduction of noise. 

  2. Size of the signal separation. The input signal should stay away from the output signal and power, the specific design printed board, there are two ways, one is a single signal flow method, the printing plates from one end of the input signal, the other end of the output; the other is ground isolation method that the size of the signal isolation between the land line. 

  3. Transmission mask. Small-signal transmission lines must use shielded cable, and single-grounded shield. Other aspects, such as symmetrical layout of components, increase the ground area and increased width of high-current copper foil (or even on the tin, etc.) are also beneficial to reduce the noise. Isolated input inductor can be installed, the output inductor installed damper

As today's digital audio output voltage swing is sufficient to achieve most of the integrated amplifier's input sensitivity, so the application just before a buffer stage, volume control and sound deployment of the role. There are two types commonly used in the first stage, one is before the op amp-type level, the higher its index, the sound quality is better, but must use high-quality potentiometers; the other is constituted by a dedicated integrated circuit before the tone volume level, such as LM1036, LM4610, TDA1524, etc., they are low cost, simple and easy system to use does not affect the sound quality of ordinary potentiometer, and the results satisfactory, fans can choose according to the actual situation.

Today, various types of integrated amplifiers have adopted the relevant protection measures, by contrast, NSC's LM series should improve some, but not foolproof, especially for the protection of fragile speakers. So, if you use more expensive speakers, I still recommend installing speaker protection and good Power Supply component.

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