Abstract: A variable gain amplifier has a large variable range of a gain with respect to an analog signal having a level changing at a high-speed. The variable gain amplifier is provided with a digital-setting-type signal attenuator having a resistor string including a plurality of resistors connected in series. A maximum attenuation-factor limiting resistor is connected between the resistor string and a ground. Each of the analog switches is connected to respective points of the resistor string. A decoder generates a control signal for selecting at least one of the analog switches, the control signal being generated based on setting data provided from an external device. A voltage across the resistor string is divided by the resistors included in the resistor string, and the divided voltage is output to an amplifier from at least one of the analog switches selected by the control signal generated by the decoder.

Abstract: A first control device controls a temperature of an object so as to make it near a first predetermined temperature. A second control device stops heating the object if a temperature thereof reaches a second predetermined temperature as a result of a temperature thereof increasing because the first control device is substantially disabled. The second predetermined temperature is higher than the first predetermined temperature.

Abstract: A method of supplying recording sheets from a plurality of paper supplying units to a reference position within a main body of an image forming apparatus which forms an image on each of the sheets supplied successively from the paper supplying units via corresponding transport paths having different lengths comprises the steps of receiving from the units data related to the lengths of the transport paths between the units and the reference position, calculating from the received data a time when a supply of a second sheet is to start from a second unit which is designated relative to a time when a first sheet supplied from a first unit which is designated reaches the reference position when it is assumed that the length of the corresponding transport path from the first paper supplying unit is zero, and driving the first and second units with timings based on the calculated times, so that a recording speed of the image forming apparatus is maintained constant regardless of the length of the transport path use