20w amplifier using ic TDA7240

The TDA7240A is a 20W bridge audio amplifier IC housed in a compact HEPTAWATT 7-pin package. The audio amplifier circuit shown here is based on the TDA7240 IC, which can deliver 20 watts of output power into a 4-ohm load. This amplifier requires minimal external components, making it simple and efficient.

Features of TDA7240A Audio Amplifier

This IC offers several advanced features, including:
20W Output Power – Provides up to 20 watts of output power in bridge-tied load (BTL) configuration.
✔ Single Power Supply – Operates on a single 12V to 18V DC power supply, making it ideal for automotive and portable applications.
✔ Short-Circuit Protection – Protects the circuit and speaker from damage due to accidental short circuits.
✔ Thermal Shutdown – Prevents overheating by automatically shutting down when the IC temperature exceeds safe limits.
✔ Low Distortion & Noise – Ensures clear and high-quality sound output with minimal interference.
✔ Standby Mode – A built-in standby function helps reduce power consumption when the amplifier is not in use.
✔ Loudspeaker Protection – Protects speakers from DC offset and sudden voltage spikes

The 20W audio amplifier circuit operates on a single 12V to 18V DC power supply, making it ideal for car audio applications. It is compact in size, requires very few components, and includes an LED power indicator to show whether the circuit is powered on or off.

Working Principle

This circuit does not include an audio/mp3 decoder but works with any external audio input signal from an MP3 player, mobile phone, or other audio sources. The TDA7240A IC does not process raw digital signals but amplifies pre-defined audio signals to the required level.

Connection Details

The audio input signal is provided at pin 3 of the IC through a coupling capacitor.
Ensure proper wiring: One terminal of the audio source output should be connected to ground, and the other should go to pin 3 of the IC.
Pin 5 and Pin 7 serve as the output terminals, which are connected to the speaker.
Pin 4 is connected to ground, and Pin 6 serves as the power supply input.
A switch can be used between Pin 2 (Standby mode) and ground to control circuit operation.

circuit diagram

Working Principle of TDA7240A

The TDA7240A functions as a bridge amplifier, meaning that it uses two internal amplifiers working in opposite phase. This BTL (Bridge-Tied Load) configuration eliminates the need for an output coupling capacitor, which enhances efficiency and allows more power delivery to the speaker.

Step-by-Step Working of TDA7240A Amplifier Circuit

Audio Signal Input – The input audio signal is provided at pin 3 through a coupling capacitor, which blocks any DC offset and allows only AC audio signals to pass.
Pre-Amplification & Gain Control – The input signal is amplified inside the IC based on its internal gain configuration.
BTL (Bridge-Tied Load) Output Stage – The amplified audio signal is sent to the output stage, where two internal amplifiers drive the speaker in push-pull mode. This configuration doubles the output voltage swing, leading to higher power output without requiring a higher power supply.
Speaker Connection – The output signal is available at pin 5 and pin 7, which connect directly to the speaker. Since it’s a BTL amplifier, there is no need for an external ground connection to the speaker.
Power Supply & Standby Mode – The amplifier operates between 12V and 18V DC. Pin 2 is used for standby mode, which can be connected to ground through a switch to reduce power consumption when the amplifier is not in use.
Protection Mechanisms – The IC has built-in thermal and short-circuit protection, which automatically shuts down the amplifier in case of excessive temperature or current flow.

Stereo Mode

For stereo sound, you can use two TDA7240A ICs, each operating as a separate channel. This setup will provide 20W + 20W stereo output. Additionally, using a suitable heatsink is recommended to prevent overheating and ensure durability.

Applications of TDA7240A Audio Amplifier

Car Audio Systems – Used in car stereos due to its low voltage operation and high efficiency.
Home Audio Amplifiers – Suitable for small home theater systems, computer speakers, and DIY audio projects.
Portable Speaker Systems – Ideal for battery-powered speaker designs due to its low power consumption.
Public Address Systems – Used in PA systems and classroom audio setups for amplifying microphone signals.