Semiconductor integrated circuit and radio communication terminal including the same

摘要

A semiconductor integrated circuit includes an operational amplifier that amplifies a voltage difference between an input voltage supplied to an inverting input terminal and a reference voltage supplied to a non-inverting input terminal and outputs an amplified signal, a feedback resistor that performs negative feedback of the amplified signal to the inverting input terminal of the operational amplifier, and a variable resistor unit that sets a current path with a first resistance value in accordance with a control signal between an external input terminal and the inverting input terminal of the operational amplifier, and sets a first alternative path with a second resistance value in accordance with the control signal between a node on the current path and a reference voltage terminal to which the reference voltage is supplied.

主权项

1. A semiconductor integrated circuit comprising:
an operational amplifier that amplifies a voltage difference between an input voltage supplied to an inverting input terminal and a reference voltage supplied to a non-inverting input terminal and outputs an amplified signal; a feedback resistor that performs negative feedback of the amplified signal to the inverting input terminal of the operational amplifier; and a variable resistor unit that sets a current path with a first resistance value in accordance with a control signal between an external input terminal and the inverting input terminal of the operational amplifier, and sets a first alternative path with a second resistance value in accordance with the control signal between a node on the current path and a reference voltage terminal to which the reference voltage is supplied, wherein the variable resistor unit includes:
a plurality of first resistor elements placed in parallel between the external input terminal and the inverting input terminal of the operational amplifier,a plurality of first switching elements respectively placed between one ends of the plurality of first resistor elements and the inverting input terminal of the operational amplifier and having a conducting state controlled based on the control signal,a plurality of resistance attenuators respectively placed between other ends of the plurality of first resistor elements, anda plurality of second switching elements respectively placed between common terminals of the plurality of resistance attenuators and the reference voltage terminal and having a conducting state controlled based on the control signal.