Introduction

In this DIY project, we will guide you through building a simple 20W audio amplifier using the TDA2020 integrated circuit (IC). The TDA2020 is a low-frequency class AB audio amplifier capable of delivering up to 14W of output power into a 4Ω load with a 14V supply. When used in a suitable configuration, this IC can easily drive small speakers, making it ideal for portable audio applications, low-power home audio systems, or even as part of a larger DIY audio project.

This particular design focuses on a clean, efficient, and straightforward build, suitable for beginners and hobbyists who are keen to get hands-on with audio electronics. No complex codes or formulas are needed for this project; we’ll focus purely on the components, their assembly, and practical advice for wiring and troubleshooting.

Components Needed

● TDA2020 Audio Amplifier IC: The heart of the circuit, this IC provides the amplification needed for driving the speaker.

● Capacitors: Various ceramic and electrolytic capacitors to filter noise and smooth power supply voltages.

● Resistors: Used for setting the gain and stabilizing the circuit.

● Speaker: A 4Ω or 8Ω speaker is ideal for this application, with power handling up to 20W.

● Power Supply: A regulated 14-18V DC power supply with sufficient current (2-3A).

● Heat Sink: The TDA2020 can get hot under load, so a heat sink is essential to keep it running cool.

● Printed Circuit Board (PCB): For mounting the components.

● Connectors and wires: For input/output and power connections.

● Optional: Potentiometer (for volume control), input jack, or enclosure for housing the circuit.

Circuit Overview

The TDA2020 is a versatile, low-distortion amplifier, and its applications in consumer audio gear are well-established. The main features of the TDA2020 include:

● Output Power: Up to 20W into a 4Ω speaker at ±18V.

● Low THD (Total Harmonic Distortion): Typically less than 0.1%, ensuring clear audio performance.

● Built-in Thermal and Short-Circuit Protection: The IC is designed to shut down in case of overheating or a short circuit, which helps protect your system.

The circuit will include the TDA2020, a few passive components for stability and filtering, a power supply section, and output connections for a speaker. We'll also include optional components like a volume control and input jack.

Step-by-Step Guide

Step 1: Preparing the Power Supply

The TDA2020 operates on a single or dual power supply, but for simplicity, we'll use a single 14V DC regulated power supply. It is important to ensure that your power supply can provide enough current—typically 2 to 3A for a 20W amplifier.

Before connecting anything to the power supply, verify the voltage with a multimeter to ensure the output is steady at 14V DC. If using a battery pack, ensure that the voltage is stable and not too low to prevent distortion or instability in the amplifier's performance.

Step 2: Mounting the TDA2020 on the PCB

To begin, you’ll need to prepare a PCB (Printed Circuit Board). You can design your own or buy a pre-made one designed for the TDA2020.

1. Solder the TDA2020 onto the PCB. Be sure to check the pinout of the IC before doing so. The TDA2020 has the following pins:

● Pin 1: Input

● Pin 2: Ground

● Pin 3: Output

● Pin 4: Negative Supply

● Pin 5: Positive Supply

● Pin 6: Ground (for internal reference)

● Pin 7: Feedback

● Pin 8: Thermal Shutdown

2. Attach a heat sink to the TDA2020’s tab (pin 4). This helps dissipate heat and prevents overheating.

Step 3: Adding Capacitors

The TDA2020 requires a couple of capacitors for stability, noise filtering, and power supply decoupling.

1. Power Supply Decoupling Capacitors: Place a 100µF electrolytic capacitor between the Vcc pin (pin 5) and ground. This helps smooth any fluctuations in the power supply voltage.

2. Feedback Capacitors: To stabilize the amplifier and ensure smooth frequency response, add a 0.1µF ceramic capacitor between pin 7 (the feedback pin) and ground.

3. Output Capacitor: An output coupling capacitor (typically 220µF) is added between pin 3 (the output) and the speaker to block any DC offset that may damage the speaker.

4. Bypass Capacitors: A 0.1µF ceramic capacitor is placed between the power supply pins (pins 5 and 4) and ground to filter high-frequency noise.

Step 4: Adding Resistors

The resistors in the circuit are primarily used to set the gain and stability of the amplifier.

1. Gain Resistor: The TDA2020 has an internal gain of around 20. However, you can adjust the gain by adding a resistor between pins 1 (input) and 7 (feedback). A typical value for this resistor is 1kΩ, but you can experiment with values between 470Ω and 2kΩ for different gain levels.

2. Input Resistor: A 10kΩ resistor between the input signal (from your audio source) and pin 1 of the TDA2020 will help filter any noise coming from the input.

Step 5: Connecting the Input and Output

1. Input: The audio signal will be fed into the amplifier via pin 1. You can use a standard 3.5mm audio jack or RCA input depending on your needs. If you’re using an RCA jack, connect the audio signal to pin 1 through the 10kΩ resistor. Ground should be connected to the ground of the power supply and the PCB.

2. Output: The output of the amplifier goes to the speaker. Connect pin 3 to the positive terminal of your speaker, while the negative terminal of the speaker should go to the ground of the power supply.

Step 6: Assembling the Power Supply and Ground Connections

Make sure the ground of the power supply is connected to the ground of the amplifier (pins 2, 6) and the ground of the speaker. This is essential to complete the circuit and ensure proper operation.

Step 7: Testing the Circuit

Before powering on the amplifier, double-check all connections, particularly the power supply connections. Verify that the capacitors and resistors are installed in the correct locations.

When you're ready, connect the power supply to the amplifier. Initially, keep the volume low on any audio source to prevent any damage to the speaker or circuit during the first test.

Power on the circuit, and slowly increase the volume of the audio source. You should hear clear audio from the speaker with a rich, full sound. If there is any distortion, double-check the capacitors and resistor values to ensure they are correct.

Step 8: Enclosure and Final Assembly

Once the amplifier is tested and functioning correctly, it’s time to assemble the circuit in an enclosure for protection and a finished look. You can either build a custom enclosure from wood or acrylic or use a pre-made metal box to house the components.

Make sure to properly mount the PCB inside the enclosure and leave sufficient airflow space around the heat sink to prevent overheating.

Optional Additions

● Volume Control: You can add a potentiometer in line with the input to allow for volume adjustment.

● Power Indicator: A simple LED can be added in parallel with the power supply to indicate when the amplifier is on.

Conclusion

By following these steps, you’ve successfully built a simple 20W audio amplifier using the TDA2020. This amplifier circuit is an excellent starting point for DIY audio enthusiasts and provides a great opportunity to explore the principles of audio amplification. With the addition of a suitable power supply and speaker, you’ll have a functional audio amplifier capable of delivering high-quality sound for various applications.

This project can also be easily customized, whether you want to add a tone control circuit, use a higher power supply for more output power, or modify the gain for different applications. As you continue with DIY audio projects, you can experiment with different amplifier ICs and configurations to suit your needs. Happy building, and enjoy the sounds of your new DIY amplifier!