Design and production of TDA1521 power amplifier

The main technical specifications of the power amplifier are as follows.

Output power: 2×12W; Frequency response: 50Hz～20kHz; Distortion: ≤0.5%.

1. circuit design

This project uses the integrated power amplifier TDAl521 to design and produce a power low-frequency power amplifier. TDA1521 is a high-quality power amplifier integrated circuit, using a nine-pin single-in-line plastic package. It has the characteristics of large output power, small gain difference between two channels, no impact sound when turning on and off the speaker, and reliable overheating, overload and short circuit protection. Output power 2x12W, distortion ≤0.1%. TDAl521A can be powered by both positive and negative power supplies or a single power supply. When powered by dual power supplies, two audio output capacitors can be omitted, resulting in better high and low sound quality. When using a single power supply, the power supply filter capacitor should be as close as possible to the power end of the integrated circuit to avoid internal self-excitation of the circuit. During production, the integrated block must be equipped with a heat sink before it can be powered on for sound testing, otherwise the integrated block will be easily damaged. The heat sink plate cannot be smaller than 200mm×100mm×2mm.

2. Circuit making

The power amplifier circuit is shown in the figure below. This circuit uses dual power supplies. Note when soldering circuits:

(1) The power supply of TDAl521 must not be connected reversely, otherwise the circuit will be burned.

(2) The heat sink must be large enough, not less than 200mm×100mm×2mm.

(3) Do not weld the speaker in the circuit, and connect the output terminal to the output terminal during assembly.

(4) In order to reduce noise, the power amplifier circuit and the preamplifier are welded on the same circuit board and as close as possible to the output end of the preamplifier.

3. Debugging of circuit

(1) Connect the power amplifier circuit to the preamplifier. Input the same AC small signal (Ui=10mV, f=1kHz) to the input terminals of the two channels, measure the voltages of the two output terminals, and observe the change range of the output voltage;

(2) Adjust the double potentiometer. Measure the maximum undistorted voltage output by the circuit;

(3) Measure the passband of the circuit.