| 摘要 |
PROBLEM TO BE SOLVED: To provide an amplifier whose dynamic range against input signal amplitude is large and whose waveform degradation is less by controlling the impedance of a variable impedance element by means of either an output voltage itself or a bottom of detected output voltage. SOLUTION: When an input voltage of a bottom detection circuit 6 is lower than its output voltage, an output voltage of a source follower constituted of a pair of P channel-type MOS transistors 7 and 8 becomes equal to the input voltage of the bottom detection circuit 6. When the input voltage of the bottom detection circuit 6 becomes higher than its output voltage, the output voltage of the source followers constituted of a pair of the P channel-type MOS transistors 7 and 8 becomes equal to the output voltage of the bottom detection circuit 6. Thus, the source follower constituted of a pair of the P channel-type MOS transistors 7 and 8 operates so that is synthesizes the input voltage and the output voltage of the bottom detection circuit 6. |
