VARIABLE GAIN AMPLIFIER

PROBLEM TO BE SOLVED: To suppress a gain error of a variable gain amplifier.SOLUTION: A variable gain amplifier has: a source-grounded transistor having a gate to which an input signal is supplied; a plurality of first cascode transistors each having a source connected to a drain of the source-grounded transistor; a second cascode transistor having a source connected to the drain of the source-grounded transistor; a first gate-grounded transistor having a source connected to the drains of the plurality of first cascode transistors, and a gate to which a constant voltage is applied; and an output load connected to the drain of the first gate-grounded transistor. The plurality of first cascode transistors and the second cascode transistors are controlled to be in a conductive state or a non-conductive state so that a drain current of the source-grounded transistor becomes constant and that a proportion of the drain currents supplied to the plurality of first cascode transistors changes.