PAM8403 mini amplifier: 2.3 x 1.8cm / 0.9 x 0.7in, compact size fits easily into small spaces in various digital devices, offering high amplification efficiency. Powered by 5V USB from computer, phone charger, or lithium battery. High efficiency up to 90%, delivers 3W (left channel) + 3W (right channel) output with 4-ohm load and 5V power supply. Class D amplifier design ensures high efficiency, maintains sound quality without thermal degradation, and eliminates the need for a heat sink. Built-in noise reduction circuit prevents popping sounds during power on/off; supports short circuit, over current, and over temperature protection. Specifications: Working Voltage: 2.5V5.5V DC (do not exceed 5.5V; observe correct polarity) Compatible Speaker: 48 ohms (4 ohms recommended); speaker power 28W Color: Green Material: PCB Package Includes: 5 x Power Amplifier Module Note: The package includes only the items listed above. Other accessories are not included. Note: Lighting conditions and monitor settings may cause slight variations in color between the image and actual product. Measurement error allowed within +/- 13 cm.