The **AVT175** is a classic DIY electronic project kit, widely known as a **Low-Power Stereo Amplifier**. It is based on the integrated circuit (IC) **TDA2822**, which is designed for portable radio and playback devices. --- ### 1. Core Component: TDA2822 IC The heart of the AVT175 is the **TDA2822** (or its variant TDA2822M). * **Type:** Dual Power Operational Amplifier. * **Function:** It takes a weak audio signal (like from a phone or MP3 player) and amplifies it to drive small speakers. * **Operating Voltage:** Typically 3V to 15V DC, making it ideal for battery-powered use. --- ### 2. Key Electronic Parts List The kit consists of the following categories of components: | Component Type | Part Value/Name | Function | | :--- | :--- | :--- | | **Integrated Circuit** | TDA2822 | The main stereo amplifier chip. | | **Resistors** | 4.7 $\Omega$ | Part of the "Zobel Network" to ensure high-frequency stability. | | **Electrolytic Caps** | 100µF - 470µF | AC coupling for output and power supply filtering. | | **Ceramic Caps** | 100nF (0.1µF) | Decoupling and noise suppression. | | **Potentiometer** | 2 x 10k$\Omega$ - 50k$\Omega$ | Volume control (usually logarithmic). | | **Connectors** | Goldpin/Screw Terminals | Input signal, Power supply, and Speaker output. | --- ### 3. Circuit Sub-Systems The AVT175 circuit is divided into three functional blocks: 1. **Input Stage:** Uses coupling capacitors to block DC voltage from the audio source, ensuring only the AC audio signal reaches the IC. 2. **Amplification Stage:** The TDA2822 increases the signal gain. The gain is usually fixed internally by the chip's architecture to minimize external part count. 3. **Output Stage:** Large electrolytic capacitors are used at the output to prevent DC current from damaging the speakers while allowing the amplified audio to pass through. ### 4. Technical Specifications * **Output Power:** Approximately $2 \times 1W$ (at 9V into $8\Omega$ speakers). * **Channel Count:** 2 (Stereo). * **Distortion (THD):** ~0.2% at low power levels. * **Quiescent Current:** Very low (~6-9mA), which preserves battery life. --- ### 5. Assembly Tips * **Orientation:** Ensure the notch on the TDA2822 IC matches the symbol on the PCB. * **Polarity:** Electrolytic capacitors are polarized; the stripe on the side indicates the negative (-) lead. * **Heat:** While this IC doesn't get very hot at low voltages, ensure it has some airflow if running at the maximum 15V.