PURPOSE: To obtain an amplifier which is equipped with only the high efficiency of a switching amplifier and only the low distortion rate of an analogue amplifier overall, by combining the amplifier, which is high-efficiency and does not perform negative feedback sufficiently and has much distortion, and the high-efficiency and low-distortion rate analogue constant-current amplifier which operates by a very low power source voltage.

CONSTITUTION: One end of load C is connected to output end a of constant-voltage amplifier A, and the other end of load C is connected to output end b of constant- current amplifier B, and the output end voltage of constant-current amplifier B is applied to the input end of constant-voltage amplifier A in negative feedback, and signals are applied to input end of constant-current amplifier B to take out the output at load C.