Sheet feeding device and printing apparatus

A sheet feeding device comprising:

• a holding portion that holds a roll formed of a wound sheet;
• a drive unit that rotates the roll held by the holding portion in a first direction in which the sheet is fed out into a conveyance path and in a second direction which is reverse to the first direction;
• a sensor that outputs an output value according to a distance between a detecting position facing a peripheral surface of the roll and the peripheral surface of the roll;
• an amplification circuit configured to amplify the output value from the sensor;
• and
• a control unit that changes an amplification factor of the amplification circuit for each of predetermined angles while the roll is rotated by the drive unit one rotation in the second direction and acquires data of output values including the output value corresponding to each amplification factor,
• wherein a plurality of amplification factors include at least a first amplification factor and a second amplification factor,
• wherein a plurality of sub-data sets corresponding to the plurality of the amplification factors, respectively, including a first sub-data set and a second sub-data set corresponding to the first amplification factor and the second amplification factor, respectively, are extracted from the data, and
• wherein the control unit determines the amplification factor to be used on the basis of the plurality of sub-data sets.