Features: Can use the computer USB port 5V power supply or using a mobile phone charger USB port 5V power supply battery power can also be used high efficiency:90% can provide 3W (left channel) +3 W (right channel) output power in the 4 load and 5V power supply conditions A class, B class amplifier such efficiency is only about 30% D class amplifier is highly respected today D class amplifier efficiency is extremely high, not because of temperature affect the sound quality but do not add heat sink and take less space noise canceling circuit was built in the amplifier board power on / off without pop noise module has a short-circuit current protection and over-temperature protection Specifications: Operating voltage: 2.5V-5.5V Speaker With:4-8ohms recommended:4 ohms Speaker Power :2-8W Size:21 x 18 x 3.4mm(L x W x H) Color:As the pics show Net weight:1g Application: LCD TVs, monitors, Laptop Portable Speakers Portable DVD players, game consoles Phone / speakerphone Package Included: 10*PAM8403 Digital Power Amplifier Board