The LA4905 is a BTL 2-channel power amplifier IC for use in car audio systems. Increases in the number of external components are held to a minimum by adopting both a signal-following type switching scheme in the amplifier's output stage power supply, and a newlydeveloped nonlinear amplifier that has nonlinear characteristics in the signal system. The power dissipation (thermal loss) in the actual operating range has been reduced to about 1/2 that of earlier class B amplifier ICs. This contributes significantly to miniaturization of the heat sink and to reduction of heating within the set.