LM1875 Power Amplifier Problem 30

Yes""Buzz""Sound is generally a power supply problem, you can appropriately increase the filter capacitor and connect the positive and negative poles to the ground with a 104 polyester, and in 1875 with 5 feet and 3 feet to the ground, also connect a 104 capacitor! If it can't be solved, there is a problem with the circuit layout of the board!

There is noise: try to short-circuit the input to ground to see if there is any, and there is a broken LM1875, if not, it is the peripheral circuit!

You didn't connect the capacitor to ground in the first place? Is it connected in series with a very small resistor between the amplifier output and ground?

That is the Rubert network to prevent self-oscillation, suggestion 1 first to see if the circuit board wiring is reasonable, pay attention to single-point grounding! 2.Whether the chip decoupling circuit is connected or not, the decoupling capacitor should be next to the chip.

3.Short-circuit the input and use the oscilloscope to see the output waveform and the power supply waveform at the same time! This may also be due to the low noise introduced by the power supply.

The 1875 has a good internal protection circuit, which is generally not easy to break. I think it's a circuit board wiring problem, or a power supply problem.

1., is the measurement of positive and negative power supply symmetrical?

2.In 1875 the 3 and 5 pin to ground connection capacitors, attention! This capacitor needs to be soldered directly to the pins to the nearest ground!

3.Try making the ground wire thicker.

4.Try connecting the common terminal (ground) of the input socket directly to the common point (ground) of the two filter electrolytic capacitors with a thick wire.

The LM1875 adopts the TO-220-5 package structure, which is shaped like a medium power tube, with small size, simple peripheral circuit, and large output power. The integrated circuit is equipped with overload, overtemperature and inductive load reverse potential safe working protection. It has exactly the same function as TDA2030 and can be directly replaced.

A typical two-channel amplifier circuit is shown in the figure below

Dual power supply circuit:

Printed circuits:

The 1875 is a mono amplifier, and if you want to do a two-channel one, you need at least two pieces, and the peripheral circuitry is the same. There are a lot of drawings on the Internet, all the same.

Let's use tda1521.

Two-channel. Check it out here.

Without the TDA2022 amplifier, the main differences between the LM1875 amplifier board and the LM3886TF are as follows:

First, the output power is different.

1. LM1875: The output power is 20W.

2. LM3886: continuous output power 68W.

Second, the sound quality characteristics are different.

1. LM1875: The sound quality is softer and easier to start, and the strength is smaller than that of LM3886.

2. LM3886: The distortion is small, and the sound quality is more layered and dynamic.

Third, the functional characteristics are different.

1. LM1875: small size, simple peripheral circuit, and large output power.

2. LM3886: large output power, protection functions (including over-voltage protection, over-temperature protection, current limit, temperature limit, and loudspeaker when switching and switching power supplies.

Shock protection, noise suppression function) is complete, there are few peripheral components, easy to make and debug, and the work is stable and reliable. Due to the simplicity and applicability of the power amplifier circuit made by hail, it is especially suitable for the production of burners and electronics enthusiasts.

Encyclopedia - lm1875

Encyclopedia - lm3886

LM1875 standard circuit, this circuit only needs to be soldered according to the components in the circuit, no need to debug.

Resistance: 1m a, 22k a, 1k a, 20k a, 1r a, "power one w".

Capacitors: One "best use stepless audio capacitor", two, 100uf two, 22uf one, one.

Simple LM1875-30W power amplifier circuit diagram.

1 The resistor is not replaced with much of a size.

1) You can push the earphones, you don't need to worry about the output level, the 1875 standard line will do.

2) Connect 1-10K resistors to each of the two channels, and then connect to the power amplifier input.

3).I didn't get it.

Double 1875 is no problem with the moon cake box for heat dissipation.

The heat dissipation mainly depends on a few points.

1. Whether there is self-excitation under no load should be ruled out first. Otherwise, the heat will only accumulate.

2 Whether the IC is in good contact with the heat sink, it is recommended to put on a layer of heat pipe, and then tighten the screws as much as possible.

3. The heat dissipation environment is kept ventilated, the proper thermal balance, and the temperature of forty or fifty degrees does not affect the sound quality, but makes it easier to keep the circuit in good condition due to a certain temperature.

4 If the fit is complete, of course, the heat is preferentially conducted through the metal to distribute the heat to the heat sink, and the thermal radiation or convection between 1875 is basically negligible.

5 Overall, turn on to maximum volume. Continuous work, the temperature rise (not the temperature is the temperature rise) is not particularly obvious, it's no problem...

If the four 1875s are close together and in a row, find a large radiator that is insulated with mica sheets or silicone gaskets, and the radiators must not be associated with the rest of the circuit, as the metal sheets of 1875 are connected to -VCC.