Variable resistance circuit, operational amplification circuit and semiconductor integrated circuit

摘要

A variable resistance circuit comprises a resistance circuit including a plurality of resistors serially connected, and a bypass circuit connected in parallel with the resistance circuit for bypassing one or more resistors selected from the plurality of resistors. The bypass circuit includes a plurality of transistors selectively turned on or off. The variable resistance value is determined by a combined resistance value of a parasitic resistance of one or more transistors being turned on and one or more resistors being bypassed as well as a combined resistance value of one or more resistors being not bypassed. The gate widths of the plurality of transistors are so set that the variable resistance value varies approximately in steps of a predetermined value. Various resistance values can be set in high precision by selectively turning on or off the plurality of transistors.