Patent ID: 8466749

Claim:
A variable gain amplifier, comprising: a source-grounded transistor, to a gate of which an input signal is supplied; a plurality of first cascode transistors, sources of which are connected to a drain of the source-grounded transistor; a second cascode transistor, a source of which is connected to the drain of the source-grounded transistor; a first gate-grounded transistor, a source of which is connected to drains of the plurality of first cascode transistors, and to a gate of which a constant voltage is applied; an output load connected to a drain of the first gate-grounded transistor; and a second gate-grounded transistor, a source of which is connected to a drain of the second cascode transistor and to a gate of which the constant voltage is applied; wherein the plurality of first cascode transistors and the second cascode transistor are put into a conducting state or a non-conducting state such that a drain current of the source-grounded transistor is constant and moreover a fraction of the drain current supplied to the plurality of first cascode transistors changes.