Digital AGC control method and feedback control apparatus

A digital AGC control method comprising:

• a first step in which an AGC unit outputs a setting value in accordance with a reference input value;
• a second step in which a control unit calculates an operation amount of a controlled object using the setting value;
• a third step in which an output unit generates an output signal representing the operation amount and outputs it to the controlled object;
• a fourth step in which a measuring unit calculates an operation measurement value of the controlled object;
• and
• a fifth step in which the measured value is input to the AGC unit,
• said first step including:
• a sixth step in which the AGC unit stores the reference input value in a first register, stores the measured value input in the fifth step in a second register, and calculates and stores in a third register a deviation between the reference input value stored in the first register and the measured value;
• a seventh step in which a number of consecutive bits, other than a sign bit, of “0” value among higher-order bits in the first register is detected;
• and
• an eighth step in which the deviation stored in the third register is shifted left by a number of bits in accordance with the number of bits detected in the seventh step to generate a deviation setting value as the setting value.