This Schematic use IC AN7102S , this is setereo amplifier and have output speaker 7,5 mW with impedance 32 Ohm . Supply need 1Volt to 3 Volt , wow this amplifier low voltage. You can use this amplifier on radio is use battery . With just one battery with voltage 1,5 Volt you can play this amplifier. See this Schematic below : Click to Enlarge Datasheet IC AN7102S Vcc = 1-3 V Pout = 2X 7,5 mW RL = 32 Ohm Ft = 20hz - 20Khz Icco = 7 mA Package = DIP-18 Manufactered = MATSUSHITA